Stabilized Ceramic Composition, Apparatus and Methods of Using the Same

ABSTRACT

In one aspect, the invention includes a refractory material, said material comprising: (i) at least 20 wt. % of a first grain mode stabilized zirconia based upon the total weight of said material, said first grain mode having a D50 grain size in the range of from 5 to 2000 μm, said stabilized zirconia including a matrix oxide stabilizer; (ii) at least 1 wt. % of a second grain mode having a D50 grain size in the range of from 0.01 μm up to not greater than one-fourth the D50 grain size of said first grain mode zirconia, based upon the total weight of said material; and (iii) at least 1 wt. % of a preservative component within at least one of said first grain mode stabilized zirconia, said second grain mode stabilized zirconia, and an optional another grain mode; wherein after sintering, said material has porosity at 20° C. in the range of from 5 to 45 vol %.

FIELD OF THE INVENTION

This invention pertains to ceramic materials, components, methods,thermal reactor apparatus and processes using the same, demonstratingimproved physical and chemical stability in refractory applications. Insome embodiments, the components may have particular utility inpyrolysis reactors such as may be used for thermally cracking,converting hydrocarbons, or for performing other high temperaturechemistry. The invention includes refractory grade ceramic componentsthat are resistive to progressive compositional degradation, therebydemonstrating improved retention of certain performance properties, suchas strength, toughness, chemical stability, and thermal stability athigh temperatures such as above 1500° C., as compared to prior artrefractory grade ceramics.

BACKGROUND OF THE INVENTION

Economical operation of high severity hydrocarbon cracking processes andequipment requires overcoming numerous competing operational andengineering challenges. The high temperatures and process stresses canexceed the long term viability of most conventional materials, includingceramics. In addition to component physical and thermal performanceconsiderations, component chemical inertness and crystalline stabilityalso become significant impediments requiring consideration. Componentdegradation and corrosion during long-term use present still furtherobstacles requiring address, particularly with regard to severehydrocarbon processing.

One problem in the art pertains to ceramic stabilizer volatility andprogressive loss of such stabilizer from the ceramic due to the severepyrolysis temperatures and cyclic temperature swings. This stabilizerloss results in progressive reduction in crystalline stability andcomponent degradation, eventually leading to premature componentfailure.

Conventional steam crackers are a common tool for cracking volatilehydrocarbons, such as ethane, propane, naphtha, and gas oil. Otherhigher severity thermal or pyrolysis reactors are also known to beuseful for cracking hydrocarbons and/or executing thermal processes,including some processes that are performed at temperatures higher thancan suitably be performed in conventional steam crackers. As compared toconventional cracking equipment and processes, higher temperaturereactions and processes typically require more complex, costly, andspecialized equipment to tolerate the intense heat and physical stressconditions. Properties such as temperature, reaction environment,component strength, and toughness limitations commonly defining upperlimits for many of the processes and facilities.

In addition to processes utilizing high temperatures (e.g., >1500° C.),processes involving high temperatures plus large cyclic temperatureswings and process fluid directional changes, such as regenerative orreverse flow reactor processes, pose even greater challenges. Forexample, the art discloses that to efficiently obtain relatively highyields of acetylene from pyrolyzing methane feed, such as in excess of75 wt. % yield, reactor temperatures in excess of 1500° C. are requiredand preferably in excess of 1600° C., with relatively short contacttimes (generally <0.1 seconds). Due to the high temperatures involved,such processes are generally limited to relatively small amounts orbatches using cyclical processes yielding a mixture of acetylene, CO,and H₂. Due to the high severity, such methane cracking processes,however, have been relatively inefficient, impractical, and of verylimited commercial value as compared to other more economical processesfor generation of acetylene. Acetylene is typically generatedcommercially by cracking feeds other than methane, which may be done atlower temperatures.

The high temperature processes (e.g., >1500° C.) have previously notscaled well and are generally only useful for relatively high-cost,specialty applications. Processes such as thermally cracking methane toacetylene have largely been commercially unattractive due in large partto thermal, chemical, and mechanical degradation of the reactorequipment, including ceramic materials used therein. Cyclic temperaturechanges and product flow direction changes impose severe physicalstrength and toughness demands upon the refractory materials at hightemperature. Such stresses and performance demands have also typicallylimited manufacturing and use of the refractory materials to relativelysimple shapes and components, such as bricks, tiles, spheres, andsimilar simple monoliths. Reactor component functions and shapes havebeen limited for high severity services.

In addition to physical temperature limitations for reactor materials,many prior art ceramic reactor materials that are relatively inert atlower temperatures become susceptible to chemical degradation, ceramiccorrosion, and/or crystalline alteration at higher temperatures, leadingto premature equipment degradation and/or process interference, such asby generation of unacceptable levels of contaminants in the process.Although high temperature regenerative pyrolysis reactors are generallyknown in the art as capable of converting or cracking hydrocarbons, theyhave not achieved widespread commercial use, due significantly to thefact that they have not been successfully scaled to a commerciallyeconomical size or useful life span as compared to less severealternatives, such as steam cracking.

The identified prior art pertaining to refractory materials forhigh-severity hydrocarbon pyrolysis dates primarily to the 1960's andearlier. However, that art merely occasionally provides generalizedlists of some exemplary materials such as ceramics, alumina, siliconcarbide, and zircon as reactor materials. These sparse, non-specificdisclosures left the art largely incapable of providing a large-scale,commercially useful reactor or reactor process. The teachings of the artwas only effective for enabling relatively small scale specialtyapplications that see vastly inferior use as compared to large scaleprocesses such as hydrocarbon steam cracking. The identified art is voidof teaching or providing a refractory ceramic material that is capableof sustaining the complex set of properties that are required forextended use in the reactive or other most-demanding regions of ahigh-severity (>1500° C.) pyrolysis reactor, such as for the commercialproduction of acetylene and/or olefins from methane or other hydrocarbonfeed. The studied art does not teach preferred crystalline structures orcompositions for particular reactor furnace uses, or for complex reactorcomponent shapes and/or functions. Multimodal ceramics are also known inthe ceramics art, as are ceramic compositions utilizing nanoparticles.However, the art remains void of teaching a ceramic or other compositionor method of preparing the same that meets the rigorous performanceproperties needed for commercial application and long-term stability inhigh temperature cyclic pyrolysis processes. Further, the desiredmaterials must maintain their formulations, crystalline structure, andcorresponding physical and chemical properties for prolonged periods oftime, at commercial scale and within the confines of an economicrequirement. The studied art is believed to be similarly deficient atteaching materials suitable for complex, irregular, relatively fragile,or functionally-shaped reactor components.

For further example, the “Wulff” process represents one of the morepreferred commercial processes for generation of acetylene. Wulffdiscloses a cyclic, regenerative furnace, preferably including stacks ofHasche tiles (see U.S. Pat. No. 2,319,679) as the heat exchange medium.However, such materials have demonstrated insufficient strength,toughness, and/or chemical inertness, and are not amenable to use ascertain desirable reactor components, such as for use as reactor fluidconduits, to facilitate large-scale commercialization. Although some ofthe “Wulff” art disclose use of various refractory materials, acommercially useful process for methane cracking or other extremehigh-temperature processes (e.g., >1500° C., >1600° C., and even >1700°C.) has not previously been achieved utilizing such materials. Theaforementioned practical obstacles have impeded large scaleimplementation of the technologies. Materials availability for hightemperature, high-stress applications is one of the most critical issuesin design and operation of large-scale, commercial, high-productivity,thermal reactors. Due to high temperatures involved in cyclic pyrolysisreactors, generally only ceramic components have the potential to meetthe materials characteristics needed in such aggressive applications.

One attempt to overcome the above listed problems involved use of a“deferred combustion” process that delayed combustion and heatgeneration until the reaction components were positioned into the coreof the reactor, thermally isolated from flow control equipment that wassubject to premature degradation. The deferred combustion, regenerativereactor process and equipment was disclosed in a U.S. patent applicationfiled Dec. 21, 2006, Ser. No. 11/643,541, entitled “Methane Conversionto Higher Hydrocarbons,” related primarily to methane feedstocks forpyrolysis systems. Although the disclosed process of the '541application effectively controls the location of combustion within thereactor, the internal reactor components must still contend with theseverely high temperatures, temperature changes, and physical stressesincurred during methane pyrolysis, particularly for a commerciallydesirable reactor life term. The refractory material comprising thereactive regions may typically be a ceramic or related refractorymaterial. In some embodiments, however, the disclosed processes andapparatus may utilize relatively complex shaped refractory components,such as a thin-walled honeycomb monolith used to conduct process fluidsthrough the reactor. Such reactors and reactor component geometries maydemand materials that have strength, toughness, chemical inertness, andother required properties that exceed the capabilities of previouslyidentified or known refractory materials under such temperature andstress conditions.

Ceramics components generally can be categorized in three materialcategories: engineering grade, insulation grade, and refractory grade.The term “engineering grade” has been applied to ceramic materials whichtypically have very low porosity, high density, relatively high thermalconductivity, and comprise a complete component or a lining. Examplesinclude dense forms of aluminum oxide (Al₂O₃), silicon nitride (Si₃N₄),silicon carbide (SiC), silicon aluminum oxynitride (SIALON), zirconiumoxide (ZrO₂), transformation-toughened zirconia (TTZ),transformation-toughened alumina (TTA), and aluminum nitride (AlN).These materials usually possess high strength and toughness, which havebeen dramatically improved to the degree that ceramics are now availablethat can compete with metals in applications previously thoughtimpossible for ceramics. Strength is a measurement of the resistance toformation of a crack or structural damage in the material when a load isapplied. Toughness is a measurement of the resistance of the material topropagation of a crack or extension of damage to the point of failure.Even though engineering grade ceramics have superior strength andtoughness at relatively low temperatures, they are relatively poor inthermal shock resistance (both strength and toughness) and many grades,such as but not limited to borides, carbides, and nitrides are notchemically stable at high temperature. Many are also not suitable foruse at the high temperatures encountered with some pyrolysis reactions.

The second category of ceramic materials is insulation grade ceramics,which are typified by relatively high porosity. Many may have fibrouscrystalline grain structures and are more porous than engineering gradeceramics, have lower density, and have lower thermal conductivity thanengineering grade ceramics. Insulating monolithic ceramics and compositeceramics are often fabricated into various forms such as rigid boards,cylinders, papers, felts, textiles, blankets, and moldables. Many areprimarily used for thermal insulation at elevated temperatures, such asup to 1700° C. A broad range of porosities and pore sizes can beproduced, depending on the intended application, but in general,insulation grade ceramics tend to be relatively porous as compared toengineering grade ceramics. Porous ceramics have many open or closedinternal pores that provide the thermal barrier properties. Often, quiteporous ceramics, such as those having porosity of greater than 50 vol. %and commonly even in excess of 90 vol. %, are used for thermalinsulation where extremely low thermal conductivity (<0.08 W/m·K) isrequired. However, insulation grade ceramics typically lack thestructural strength and functional toughness needed for the internalcomponents of many pyrolysis reactors and processes. Insulation gradeceramics typically are recognized as having a flexural strength ortoughness of less than about 4 Kpsi (27.6 MPa) and often of less thaneven 1 Kpsi (6.9 MPa). Also, the insulation properties of porousceramics may tend to degrade as the pores may fill with cokeaccumulation.

The third generally recognized category of ceramic materials isrefractory grade ceramics. Many refractory grade ceramics typically haveporosity, strength, and toughness properties intermediate to suchproperties in engineering grade and insulation grade. Refractory gradeceramics typically have thermal shock resistance properties similar tosome insulation grade ceramics but higher than engineering gradeceramics. Conversely, refractory grade ceramics typically lack thestrength and toughness of engineering grades ceramics, but whichproperties exceed those of insulation grade ceramics. However, typicallyas strength increases, thermal shock resistance and related propertiesare compromised. All relevant properties must be considered whenselecting a ceramic for a particular application.

As compared to insulation grade ceramics, refractory grade ceramics tendto be stronger across broader temperature ranges. Refractory gradeceramics also generally tend to be more resistant to thermal shock thanengineering grade ceramics. However, while some ceramics tend to besomewhat inert or chemically stable at moderately elevated temperatures,many ceramics become chemically and/or structurally unstable at severelyelevated temperatures, tending to degrade and corrode within undesirablyshort periods of time, rendering them unsuitable for some applications.Exemplary chemically and/or thermally unstable ceramics include certainsilicas, aluminas, borides, carbides, and nitrides. Also, somerefractory grade ceramics are known to possess lower thermalconductivities and coefficients of expansion than certain otherrefractory or engineering grade ceramics. Refractory grade ceramics arealso known to undergo alterations in crystalline structure at elevatedtemperatures. Such alterations can result in changes in bulk volumewhich can result in creation of stress fractures and/or cleavage planeswhich can reduce the material's strength or performance properties.

Some advanced engineering ceramics, such as aluminas, zirconias, andsilica, such as SiC and Si₃N₄, also provide superior strength, but theirthermal shock resistance in grossly inadequate. Moreover, these siliconbased ceramics can not be used at high temperatures (i.e. >1500° C.) dueto high temperature oxidation issues. On the other end of the spectrumlie the insulation grade ceramics. These ceramics offer excellentthermal shock resistance, but they fall quite short of the requiredstrength performance.

Zirconia is a crystalline material that is commonly used in certainceramics, also having thermal application. However, zirconia undergoes acrystalline change at different temperatures in the way its atoms arestacked (polymorphic transformation). Zirconia has a monoclinic crystalstructure between room temperature and about 1200° C. Above about 1200°C., zirconia converts to a tetragonal crystal structure. At a stillhigher temperature, such as above 2370° C., zirconia changes fromtetragonal to cubic structure and melts at 2715° C. Thesetransformations are accompanied by greater than one percent volumetricshrinkage during heating and equivalent expansion during cooling. Thevolumetric changes associated with alterations in crystalline structurecan produce crystalline fractures or cleavages along grain boundaries.In polycrystalline zirconia, this tetragonal-monoclinic transitionresults in a reduction in strength and potential catastrophic failure ofthe component. Stabilizers, such as yttria and some metal oxides are canbe into the crystal structure to arrest or prevent the crystallineshifts, rending the crystal structure across a more broad temperaturespectrum.

However, it has recently been learned that extended exposure ofstabilized ceramic components, such as but not limited to stabilizedzirconias, to high temperature processes and severe environments canresult in gradual evacuation or loss of the stabilizer component fromthe ceramic crystals. This loss undesirably results in progressingtemperature-related re-alteration of the crystal structure over time,further leading to onset of the aforementioned cleaving and fracturingproblems. Such stabilizer material loss and crystal alteration result ina corresponding degradation and reduction in life expectancy of thecomponent, due to compromised performance properties.

The pyrolysis art needs a stabilized ceramic composition or materialthat provides the desirable set of performance properties and that cansustain those properties for a commercially meaningful period of use, byresisting loss of stabilizer, maintaining crystalline stability, andenduring prolonged exposure to high severity temperatures, substantialtemperature swing cycles, cyclic flows of combustion and reactionmaterials. The desired materials must concurrently provide the neededstructural integrity, crystalline stability, relatively high heattransfer capability, and chemical inertness required for large scale,commercial, high productivity applications. Unavailability of suchmaterials, components, and associated processes has been one of the mostcritical impediments against large scale, commercial adoption andapplication of many high temperature pyrolysis and chemistry processesand apparatus.

SUMMARY OF THE INVENTION

The present invention provides materials, compositions, components,reactors, processes, and methods that overcome the aforementioneddeficiencies. Particularly, the present inventions include materials,components, and methods that among other attributes rectify the loss ofstabilizer and corresponding crystalline instability problems. Inventiveembodiments and aspects may have broad application to stabilizingceramic materials for use in high temperature pyrolysis and/or highlyactive environments, resulting in extended component and equipment lifeexpectancy and predictability. For example, the present inventions mayhave particular application for use in high temperature pyrolysisreactors and furnaces, and more particularly with such apparatus andprocesses involving high temperatures, aggressive environments, or otherthermodynamically active reactions.

In one aspect, the invention includes but is not limited to ceramiccomponents and pyrolysis reactors utilizing such components, includingbut not limited to manufacturing processes and uses related thereto.According to the present invention, the unique combination of stabilizedzirconia, distribution of multiple grain sizes, stabilization of thegrains, presence of a preservative component, and prescribed porosity isbelieved to provide inventive materials and components differing fromanything previously known in pyrolysis and refractory arts.

In one aspect, the invention includes a refractory material comprising:(i) at least 20 wt. % of a first grain mode based upon the total weightof the refractory material, the first grain mode comprising stabilizedzirconia, the first grain mode stabilized zirconia having a D50 grainsize in the range of from 5 to 2000 μm (some embodiments in the range offrom 5 to 800 μm), the stabilized zirconia including a matrix oxidestabilizer; (ii) at least 1 wt. % of a second grain mode having a D50grain size in the range of from 0.01 μm up to not greater thanone-fourth the D50 grain size of the first grain mode stabilizedzirconia (the second grain mode is herein selected as the “fine” gritsize mode, relative to the size of the larger or more “coarse” gritfirst grain mode), based upon the total weight of the refractorymaterial; and (iii) at least 1 wt. % of a preservative component;wherein after sintering the material has porosity at 20° C. in the rangeof from 5 to 45 vol %. The preservative component may be provided withinone or more of (a) the first grain mode, (b) the second grain mode,and/or (c) an optional another grain mode, and the amount of the atleast 1 wt. % of the preservative component is determined based upon theaggregate of preservative component within the refractory material. Thatis, the at least 1 wt. % minimum is not limited to a minimum amount ineach mode, but instead to an aggregate amount within the entirety of therefractory material. The term “zirconia” is defined broadly to includenot only zirconium oxide, as in many embodiments the crystals or grainscomprising the refractory material are primarily made up on zirconiumoxide crystals, but also the term zirconia as used herein also includesthe element zirconium and other compounds including zirconium, asappropriate.

In many embodiments, the first or coarse grain mode stabilized zirconiais a partially stabilized zirconium oxide, a.k.a. herein as partiallystabilized zirconia. The first grain mode zirconia stabilizer mayinclude a matrix oxide stabilizer, such as a metal oxide. In manyembodiments, the fine or second grain mode includes a stabilizedzirconia. In many other embodiments, the second grain mode includes oreven consists essentially of the preservative component. In someembodiments, the preservative component is provided primarily within thesecond grain mode. In still other embodiments, the preservativecomponent is provided within the first grain mode, as a separate grainmode, or in a combination of both the first grain mode, second grainmode, and/or a distinct grain mode, including but not limited toembodiments where the another or distinct grain mode consistsessentially of the preservative component. As used herein, the terms“grit,” “particle” and “grain” generally may be used interchangeably,except as otherwise indicated.

In other embodiments, the second grain mode comprises a fully stabilizedzirconia stabilized by a second grain mode zirconia stabilizer, whereinat least a portion of the second grain mode zirconia stabilizer alsofunctions as the preservative component. In such embodiments, preferablythe second grain zirconia stabilizer is present in an amount sufficientto at least partially stabilize and in some embodiments more preferablyto fully stabilize, the second grain mode ceramic and also,surprisingly, with the remainder or excess amount of stabilizer in thesecond mode functioning as the preservative component to help the matrixoxide stabilizer to stabilize the first grain mode matrix withoutrendering the first grain matrix to be a fully stabilized. Sometimes,having a partially stabilized first grain mode may be preferable due tothe superior physical and thermal performance properties offered by someof such embodiments. Therefore, it may be preferred sometimes to providethe preservative component primarily within the second grain mode,instead of within the first grain mode, such that the first grain modecan remain substantially partially stabilized. In still otherembodiments, however, the first grain mode may also be fully stabilizedand still provide the desired physical and thermal performanceproperties.

Surprisingly, providing a fully stabilized zirconia within the material,such as for example within the second grain mode, has been found toprovide a stabilizing function within the first grain mode for prolongedperiods of exposure or use, particularly when the second grain modestabilizer is present in an amount in excess of the amount required tomerely fully stabilize the second grain mode. In some embodiments, thesecond grain mode zirconia stabilizer and second grain mode preservativecomponent each comprise substantially the same materials or compounds ascomprise the first grain matrix oxide stabilizer.

According to some embodiments, the second grain mode comprises a fullystabilized zirconia, the second grain fully stabilized zirconiastabilized by at least 14 wt. % of a second grain mode zirconiastabilizer based upon the weight of the second grain stabilizedzirconia, wherein at least a portion of the second grain zirconiastabilizer within the fully stabilized second grain zirconia functionsas the preservative component. In other of such embodiments, the secondgrain mode also further comprises a preservative component that alsofunctions as the preservative component. Often, both excess modestabilizer and preservative component comprise the same material andperform the same function of stabilizing the first grain mode of therefractory material so as to overcome the progressive loss of stabilizertherefrom due to the high temperature pyrolysis.

In still other embodiments, the second grain mode comprises at least 1wt. % of preservative component, or for example at least 5 wt. %, 10 wt.%, 14 wt. %, 15 wt. %, 20 wt. %, 50 wt. %, 80 wt. %, 90 wt. %, orsubstantially 100 wt. % preservative component, based upon the weight ofthe second grain mode. The amount of preservative component is definedas that amount of stabilizer material present in the ceramic material orcomponent that is in addition to the amount of such stabilizer materialthat is actively, initially engaged or employed in stabilizing thestructure of the respective zirconia-containing mode or modes in whichit is provided. For example, when a second grain mode stabilizedzirconia is present, typically the second grain zirconia is a fullystabilized zirconia, stabilized by at least 14 wt. % of second grainmatrix stabilizer. As only a fraction of the 14 wt. % is needed to atleast partially stabilize the second grain mode stabilized zirconia, theextra amount of stabilizer is expendable for use or function as thepreservative component without compromising the stability of the secondgrain mode crystal structure. It is not prohibitive or detrimental topracticing or making the invention that determining exactly how much ofthe fully stabilizing material or stabilizer is ambiguous or difficultto determine, so long as the total amount present in the second moderenders the second mode fully stabilized. It is sufficient to havelearned that a fully stabilized second mode can offset the progressiveloss of stabilizer from the first grain mode structure during prolongeduse. The preservative component portion thus includes that portion ofthe stabilizer that is inn excess of the amount of stabilizer actuallyutilized in stabilizing the second grain zirconia matrix. It has beenlearned that surprisingly, a portion of the 14 wt. % minimum in a fullystabilized zirconia is useful to function as the preservative component.In many embodiments, the preservative component includes or issubstantially the same compounds as comprise the first grain matrixoxide stabilizer such that the stabilizers are fully mutuallycompatible. (Weight percents are the amount of a component after initialsintering for at least ten minutes at a temperature of at least 1500°C., as appropriate, unless otherwise specified.)

In some embodiments, the second grain mode may comprise only a fractionby weight of fully stabilized zirconia or may not even comprise anystabilized zirconia at all, such that the second grain mode is comprisedof at least 50 wt. % or substantially completely (at least 90 wt. %) orconsists essentially of (at least 99 wt. % or even substantially 100 wt.%) the preservative oxide, based upon the weight of the second grainmode.

In still other embodiments, the inventive formed ceramic componentsinclude a flexural strength (modulus of rupture, MOR) of at least 6 kpsiand a normalized thermal shock resistance rating of at least four (4),as described herein. In other embodiments, the inventive formed ceramiccomponents provide an MOR of at least 6 kpsi, while still otherembodiments include MOR of at least 10 kpsi. The inventive componentsmay also include a normalized thermal shock resistance rating of atleast four (4) and preferably at least five (5).

In yet other aspects, the invention includes process for the manufactureof a hydrocarbon product from a hydrocarbon feed using a pyrolysisreactor, the process comprising the steps of: (a) providing a pyrolysisreactor with a reactive region comprising a refractory material thatincludes: (i) at least 20 wt. % of a first grain mode based upon thetotal weight of the refractory material, the first grain mode comprisingstabilized zirconia having a D50 grain size in the range of from 5 to800 μm, the stabilized zirconia including a matrix oxide stabilizer;(ii) at least 1 wt. % of a second grain mode having a D50 grain size inthe range of from 0.01 μm up to not greater than one-fourth the D50grain size of the first grain mode stabilized zirconia, based upon thetotal weight of the refractory material; and (iii) at least 1 wt. % of apreservative component within the aggregate of at least one of (a) thefirst grain mode, (b) the second grain mode, and (c) an optional anothergrain mode; wherein after sintering, the material has porosity at 20° C.in the range of from 5 to 45 vol %; (b) heating the reactive region to atemperature of at least 1500° C. to create a heated region; and (c)feeding a hydrocarbon feed into the heated region to pyrolyze thehydrocarbon feed and create a pyrolyzed hydrocarbon product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an SEM photograph of an exemplary, sintered (FIG. 1a) and annealed (FIG. 1 b), ceramic component according to oneembodiment of the invention.

FIG. 2 provides photographic examples of stress cracking of variousceramic samples, each machine graded and ranked with a qualitative valuefrom 1 to 5 to illustrate corresponding normalized thermal shockresistance.

DETAILED DESCRIPTION

The present invention relates to advanced refractory type ceramics anduses for the same. In various aspects, the invention includes materials,components, apparatus, and processes having particular application foruse with pyrolysis reactors for performing high temperature(e.g., >1500° C.) chemistry, conversions, cracking, and/or thermalalteration of feeds such as but not limited to hydrocarbon feeds. Theinventive aspects include but are not limited to ceramic components andapparatus using the same that may have improved high temperaturestability, prolonged life expectancy, and/or sustained performanceproperties that may exceed the life expectancy of one or more of suchproperties as compared to previously known ceramics.

The inventive aspects may have particular utility that facilitatesenhanced large-scale commercialization of high temperature pyrolysisconversion processes. Exemplary suitable processes may include but arenot limited to high-temperature pyrolysis reactor conversion of methanefeed to acetylene or olefins, and coal gasification processes. Exemplarysuitable apparatus may include but are not limited to pyrolysisreactors, reverse flow reactors, regenerative reactors, deferredcombustion reactors, gasification reactors, syngas reactors, and steamcracking reactors and furnaces. Other exemplary inventive components mayinclude but are not limited to reactor components and apparatus thatfeature engineered or otherwise particularly designed shapes, functions,configurations, intricacies, or irregular geometries that benefit fromimproved strength and shock resistance at high temperatures(e.g., >1500° C.). Such improvements may also lead to improved processesrelated thereto.

In one aspect, the present invention provides a crystal or graincomposition and structure resistive to progressive loss of stabilizer,thereby preserving the crystalline structural of certain multimodal,zirconia-based ceramic materials or components exposed to hightemperature and/or highly reactive environments, so as to extend theuseful service life of such components. Exemplary properties benefitingfrom the enhanced stabilization may include certain performanceproperties such as but not limited to flexural strength, normalizedthermal shock resistance (MOR), and chemical stability at hightemperature, as compared to such collective properties of previous art.Such improvements may in turn lead to prolonged component run-life,improved process and apparatus economics, and large-scalecommercialization of processes and apparatus that were previouslytechnically and/or economically disadvantaged due to unacceptablecomponent life.

The present invention provides zirconia ceramic compositions that areresistive to stabilizer loss, can maintain crystalline stability, andcan endure prolonged exposure to high temperatures, substantialtemperature swing cycles, and cyclic flows of combustion and reactionmaterials. The present invention includes a ceramic composition havingat least a two-component grain size distribution, such as but notlimited to a multimodal (e.g., bimodal, trimodal, etc.) graindistribution. It also includes a prescribed porosity range to providehigh strength, and preferably a minimum fracture toughness, and thermalshock resistance. The “two-component” grain distribution sizes and term“multimodal” are not intended to limit the invention or graindistribution only to a type of distribution curve exhibiting two or moredistinct peaks, although such is within scope. The inventivedistribution and term multimodal also includes a substantially singlepeak curve covering a size distribution within the claimed particle sizeranges. In more simple terms, the inventive grain distribution includesa generally larger size first distribution of grains and generallysmaller second distribution of grains, the first distribution beingcoarser in size than the second distribution, as further defined herein.The multiple-size grain distribution facilitates increased grain packingdensity, within the prescribed range of particle sizes, whilefacilitating the presence of porosity within a prescribed range.

The inventive materials also include a preservative component to offset,replace, and/or compensate for the progressive degradation problem,thereby maintaining crystallinity for an extended duration as comparedto such compositions not including such preservative component. Arelatively coarse, first grain mode provides a stabilized zirconiamatrix, preferably a partially stabilized zirconia matrix, stabilized bya matrix oxide stabilizer. A relatively fine, second grain mode mixed inwith the first grain mode provides increased particle packing density,reinforcing the first grain matrix, and sometimes preferably providesthe preservative component.

The inventive, improved structural and chemical stability and prolongedlife is attributable at least in part to the presence of thepreservative component within at least one of the modes of themulti-modal structure, preferably the second grit mode but alternativelyin one or more of the larger grit mode or as a separate grit mode. Insome embodiments, the preservative component may be present throughoutall modes or as a distinct mode. The preservative component ispreferably substantially evenly distributed throughout the modes inwhich it is present. The preservative component stabilizes the crystalstructure across the broad spectrum of the relevant temperature range,as well as simultaneously contributing to the core physical propertiesof the ceramic. The improved performance characteristics may be also beattributable at least in part to one or more of various inventivematerial characteristics, such as but not limited to, the multimodalparticle sizes and distribution, particle arrangement, particle materialselection, degree of stabilization, manufacturing methods and techniquesused, porosity, and combinations thereof.

The inventive materials may be provided, for example, in one or moreregenerative reactor beds or cores that are useful for carrying out ahigh temperature chemical reaction. The inventive ceramic componentsalso may be used in construction of one or more reactor embodiments,components, or regions of the reactor system, and may be ofsubstantially any suitable geometry, form or shape, such as but notlimited to spheres, beads, honeycomb materials, tubes, extrudedmonoliths, bricks, tiles, and other refractory components that areexposed to high temperature. The sustained strength and relativeinertness properties of the inventive materials may provide for a widerrange of component geometries and function than previously available inthe art, again also leading to process improvements.

In one aspect, the inventive components and materials comprise zirconia(ZrO₂) based ceramics, particularly stabilized zirconia, and oftenpartially and/or fully stabilized zirconia. Preferably, the zirconiamaterial includes a diversity of grain sizes, such as, for example, in amultimodal grain configuration, comprising at least a first grain mode(e.g., a “coarse” mode, as compared to the second mode), with the firstgrain mode including a stabilized zirconia, preferably a partiallystabilized zirconia. Preferably, the zirconia base ceramic also includea relatively smaller, second grain mode (a “fine” mode), which may ormay not include a zirconia, but which in many preferred embodimentsincludes at least the preservative component. In some alternativeembodiments, the preservative component may be included within thecoarse grain mode, as a distinct mode, or in combinations thereof Inaddition to the first and second modes, other modes or additives mayalso be included within the material. According to the some preferredmodes however, the second grain mode includes the preservativecomponent, which may function to at least in part support or stabilizethe crystal structure and constituent composition of the more coarsefirst grain mode. In many embodiments it may be preferred that thecoarse grain mode zirconia is partially stabilized and not fullystabilized, to benefit from the enhanced mechanical properties affordedby partially stabilized zirconias. Adding the preservative componentwithin the coarse or first grain mode may risk undesirably fullystabilizing the coarse grit mode. However, if such embodiment isacceptable for the intended application, then the preservative componentmay be provided exclusively within the coarse first grain mode oradditionally within the coarse grain mode along with the second grainmode.

As discussed previously, the crystal structure and correspondingcrystalline matrix of zirconia ceramics may be temperature-stabilizedthrough addition of a stabilizing compound or element within theceramic's composition. Such additives are referred to as “stabilizers.”The present invention provides a functionally distinct stabilizingcomponent referred to herein as a “preservative component,” which inmany embodiments may be provided within or as a component of the secondgrain matrix. Although the total mechanism of protection may not befully understood, it is believed that the preservative component maypreferably be added into or provided as the second grain mode to permitdesign and use of a first grain mode formulation that maximizes thedesirable performance properties (e.g., via partial stabilization)without compromising the same due to the presence of a potentiallyperformance compromising compound or constituent within the first grainmode. Thereby, the second grain mode preservative component ispreferably coated upon and/or diffused into the first grain mode, bothduring initial sintering and on-going during use, forming apreservative-component-rich surface layer on the first grain mode. Thecoated surface layer thereby may desirably contain a higherconcentration of the preservative component than that in the interior ofthe first grain mode crystals or particles. Thereby, the interior of thefirst mode structure may preferably remain partially stabilized, but yetalso protected from premature or progressive degradation or loss of thestabilizer therein. The preservative component typically positions atthe grain boundaries and grain surfaces. The stabilizer may tend to actsacrificially, passively, or otherwise to prevent loss or dissociationof the stabilizer or stabilizer effects. The preservative component-richsurface layer provides a higher thermodynamic activity level ofpreservative component than the interior of the first grain mode andthereby suppresses the progressive migration or loss of the preservativecomponent from within the interior of the first grain mode. Thepreservative component-rich surface layer on the particles, preferablyprimarily on the coarse or first grain mode particles, facilitatesimproved chemical stability and the interior of the first grain moderetains proper stabilizer concentration, providing first or coarse modezirconia crystal stability over extended duration of use. As mentionedpreviously, however, for applications where maintaining a partiallystabilized coarse or first grain mode is not necessary, the preservativecomponent may be included within the first grain mode, exclusively oradditionally with respect to the second grain mode. In otherembodiments, the preservative component may comprise a grain modequantifiably distinct from the first and second modes.

Ceramic stabilizing components that may be suitable for use as eitherthe first grain matrix oxide stabilizers, the second grit mode's secondgrain stabilizer, and/or as the preservative component include at leastone weight percent, based upon the total weight of zirconia within suchrespective mode, of one or more of various stabilizing compounds,including yttrium-containing compounds, MgO, CaO, Y₂O₃, CeO₂, andmixtures thereof Chemical addition of such stabilizer or preservativecomponent may thereby result in partial formation of “cubic” zirconiacrystal structure that is relatively crystalline-stable over thecomplete temperature range and does not undergo the detrimental thermalphase transformation. In some embodiments, such “stabilized zirconia”thereby includes at least one wt percent of stabilizer, in otherembodiments at least two weight percent of stabilizer, and in stillother embodiments a stabilized zirconia may include at least four weightpercent of such stabilizer. For example, addition of about 16˜27 molepercent (˜25-45 wt. %) CaO stabilizer well mixed or dispersed within aZrO₂ (zirconia) compound will generally “fully” stabilize the resultingzirconia ceramic material. This stabilization can render the zirconiastructure into a cubic crystalline structure that remains in thatstructure over the relevant, broad temperature range, whereasunstabilized zirconias can change their crystal structure and weaken athigh temperature. Other stabilizers require different percentages tofully stabilize a zirconia. For further example, about 8 mole percent(˜14 wt. %) of Y₂O₃ mixed into the ZrO₂ provides a fully stabilized,cubic crystalline structure that is stable over the relevant temperaturerange, such as up to 2260° C. As a still further example, the criticalconcentration of MgO is about 12 mole percent (˜20 wt. %) for fullstabilization of a zirconia.

In some embodiments, the multimodal stabilized ceramic may furthercomprise one or more “secondary oxides” selected from the groupconsisting of Al, Si, Mg, Ca, Y, Fe, Mn, Ni, Co, Cr, Ti, Hf, V, Nb, Ta,Mo, W, Sc, La, and Ce, and mixtures thereof The secondary oxides may bemerely incidentally present, such as via contamination or as a result ofthe manufacturing process. The secondary oxides may also be purposefullyadded, such as to improve certain properties or uses, e.g., such asprocessability during manufacture; or may be generated and deposited asa bi-product from the thermal process and other materials present. Theamount of secondary oxides in the stabilized zirconia formed componentmay typically range from virtually none present up to 10 wt. %, or from0.001 wt. % present up to 10 wt. %, or in some embodiments from 0.01 wt.% to 5 wt. %, or in still other embodiments from 0.1 to 3 wt. %, basedon the weight of the formed stabilized zirconia component.

Zirconia containing sufficient stabilizer to render complete orsubstantially complete crystallization shift to cubic structure and azirconia having an amount of stabilizer in excess thereof, is considereda “fully stabilized zirconia.” In contrast, addition of less stabilizerthan the amount required to create a fully cubic-crystalline Zirconiastructure renders the zirconia structure a mixture of cubic andmonoclinic phases and/or cubic and tetragonal crystal phases. Zirconiacontaining such limited or lesser amount of stabilizer additive suchthat there remains at least more than an incidental amount of monoclinicand/or tetragonal crystals, is referred to herein as “partiallystabilized zirconia.” The term partially stabilized zirconia is thusdefined to include substantially any stabilized zirconia that has atleast one weight percent of stabilizer but an insufficient amount ofstabilizer to render a fully cubic-crystalline zirconia in substantiallythe whole zirconia. In yet another example, a stabilized zirconia mayinclude a fraction of a percent of at least one of such stabilizer andanother fraction of a percent of another of such stabilizer, such thatthe combined fractions make up at least one weight percent of the totalweight of the zirconia and such additive. The terms “stability” or“stabilized” as used herein refers to the ceramic component's ormatrix's ability to retain its crystallization structure in the presenceof chemically reducing environments and across the relevant broadspectrum of relevant operating temperature.

For purposes of this invention, it may be considered that as thepercentage of stabilizer increases from roughly none present towardincreasing stabilizer presence and corresponding increased stabilizationfrom partial toward full stabilization, the key strength and toughnessproperties generally tend to improve through the partial stabilizationrange. However, at some point approaching substantially complete cubiccrystallization or full stabilization, these important strength andtoughness properties may tend to digress slightly or become slightlyreduced, across a broad temperature spectrum, as compared to suchproperties in a partially stabilized zirconia that has a mixture ofcubic, monoclinic, and/or tetragonal crystals. Depending upon thedesired application, however, the full or more-fully stabilized zirconiamay still be useful for some intended applications, while for many otherapplications the generally tougher and more fracture-resistant partiallystabilized zirconia will be preferable, as explained below in moredetail. In addition to degree of stabilization, the stabilizedzirconia's performance may also be affected to varying degrees by otherfactors, such as grain size, grain distribution, packing density,stabilizer selection, processing additives, etc. By adding lessstabilizer to the zirconia compound than the amount of such stabilizerrequired to completely stabilize all of the zirconia crystals (that is,“partial stabilization”), and also preferably by careful control ofparticle sizing, distribution, and processing, mixtures of thestabilized cubic phase and the unstable monoclinic phase are achievedthat have very high fracture toughness.

However, as discussed above, it has recently been learned that extendedexposure of stabilized refractory ceramic components, such as but notlimited to stabilized zirconias, to high temperature processes andsevere environments can result in progressive loss of stabilizer fromthe ceramic crystals, resulting in undesirable temperature-relatedre-alteration of the crystal structure over time. Loss of stabilizer orreduction in stabilizer activity from a stabilized coarse grain modematrix can result in alteration and degradation of crystal matrixstructure and result in a corresponding progressive digression in keyproperties, such as but not limited to, thermal shock resistance and/orflexural strength. Under certain conditions, some stabilizers may, to avarying extent, tend to dissociate out of a stabilized zirconia underhigh temperature and/or reducing conditions, rendering portions of theceramic component essentially stabilizer-free or less stabilized thanbefore such loss. It has also been recently learned that MgO and CaO maytend to dissociate more readily than yttrium-based stabilizers, but allstabilizers have some tendency to disassociate at temperatures in excessof 1500° C. Unfortunately, unstabilized or substantially unstabilizedzirconia is unusable in many high stress applications since it goesthrough the detrimental phase transitions during heating and coolingcycles and becomes susceptible to unacceptable levels of stresscracking.

Surprisingly, it has recently been learned that it is possible toinhibit the loss from or to replace or otherwise retain the activitylevel of the lost stabilizer in, the zirconia matrix. The inventivematerials preserve the crystalline matrix composition for an extendedoperational duration or life expectancy as compared to such structuresthat are not preserved according to this invention. In some embodiments,the extended stability is achieved in the first grain mode at least inpart by the presence of a surplus or excess amount of stabilizer withinthe second grain mode. The relevant surplus or excess amount ofstabilizer (e.g., the “preservative component”) within one grain mode,such as within the second grain mode, is that amount or portion ofstabilizer that is additional to or in excess of the portion of suchstabilizer that is initially engaged in stabilizing or providing thedesired crystal structure of the respective grain mode. In manypreferred embodiments having no second grain mode stabilized ceramicpresent, then substantially all of composition of such second grain modeincludes the preservative component.

To prevent the problematic occurrence of an unstabilized first grainceramic matrix due to the described loss or dissociation of stabilizertherefrom, the present invention includes an abundance of stabilizerwithin the material or component that functions as a preservative agent.In many embodiments, the preservative component is provided within thesecond grain mode, although such additive may also be included withinother grain modes, or provided within the mixture as its own definable,distinct grain mode. This preservative component may be in the form ofan oxide or other chemical compound, such as but not limited to calciumoxide or yttrium oxide, yttrium sulfate, yttrium nitrate, etc, or inneat form such as substantially pure calcium or yttrium, or in the formof a fully stabilized ceramic having a amount of stabilizer in excess ofthe amount needed to partially stabilize the ceramic crystal. (It isnoted that generally, pure elemental forms of metals such as yttria willgenerally convert to an oxide during sintering, but such pure forms maystill be present in lesser concentrations or in non-fully-sinteredcompositions.) An exemplary stabilized ceramic having such excessstabilizer may be, for example, a fully stabilized zirconia. Since thestabilized ceramic is slightly tougher and stronger when partiallystabilized than fully stabilized, the fine mode fully stabilized ceramiccan function as the preservative component by donating some stabilizeror providing some shielding or stabilizing activity to the more coarse,preferably partially stabilized first grain mode regions whereinprogressive loss of stabilizer might be most detrimental to performanceproperties. Alternatively, the preservative component portion of thefully stabilized zirconia of the second mode may function to increasethe stabilizer activity in the adjacent first mode area that may havelost stabilizer, without compromising strength properties in eithergrain mode.

One method of introducing excess stabilizer or preservative componentmay be, for example, to provide excessive amounts of stabilizer orpreservative component within the second grit mode, such as via a fullystabilized ceramic or a fully stabilized ceramic having an excess ofstabilizer therein. Another method of introducing preservative componentis, for example, to provide a stabilizer/preservative component as adistinct component, such as in the form of an oxide, neat element, ormixtures thereof, which may be in lieu of or in addition to a stabilizedceramic (e.g., fully stabilized zirconia) in the second grit mode. Thepreservative component may thereby boost or supplement the chemicalactivity of first mode stabilizer during sintering and use, to accountfor or suppress progressive dissociation of stabilizer, thus prolongingzirconia crystal stability. Thereby, the inventive materials and methodsextend the life span of the stabilized zirconia component and associatedprocesses.

Two key materials properties are identified as having significantimportance with regard to the high-severity performance of ceramics inthermal process reactors and their corresponding suitability forapplication in large scale thermal processes; namely, thermal shockresistance and mechanical flexural strength. Other properties, such asbut not limited to crystalline/chemical stability at high temperatureand toughness are also important and must be considered when selectingan appropriate ceramic materials or components for an application.Retention or maintenance of these key and other properties over theuseful life of the ceramic component is typically desirable. With regardto maintaining longevity of such properties in components, one of themost important factors is the crystalline/chemical stability at hightemperatures. The suitably fabricated component must retain its thermalshock resistance and mechanical flexural strength over a suitable lifespan by not prematurely degrading or undergoing crystalline alteration,such as due to loss of stabilizer. The instant inventions incorporateparticular features that function to maintain or preserve thecrystalline stability, thermal shock resistance, and mechanical flexuralstrength (MOR), and possibly other related properties, for extendedperiods of time as compared to the useful duration of one or more ofsuch properties in materials lacking the inventive preservativefeatures.

Regarding the two above-referenced important performance properties,(thermal shock resistance and mechanical flexural strength), thermalshock resistance of a ceramic component can be defined as the maximumchange in temperature that the material can withstand without failure orexcessive damage. Thermal shock resistance is an evaluated parameter butnot a material property. Description of thermal shock resistance maydepend upon the type of thermal cycle, component geometry, and strengthas well as on material properties or factors. Simplified mathematicalexpressions relying upon a variety of assumptions can be used todescribe material performance under a set of conditions. Alternatively,much more complex analyses may be performed using numerical analysismethods such as finite element and stress-strain analysis. However, formaterials performance comparison purposes a qualitative or directcomparative analysis is also useful and more practical. Thermal shockresistance may be evaluated by means of rapid water quench experimentssuch as illustrated in ASTM C1525. Thermal shock damage results in amaterial from buildup of thermal and physical stresses, usually duringrapid heating or rapid cooling.

For example, the ASTM C1525 thermal shock resistance test method buildson the experimental principle of rapid quenching of a test specimen(e.g., 1″×1″×⅛″ square, or 2.54 cm×2.54 cm×0.32 cm square) from anelevated temperature (e.g., 1100° C.) into a water bath at roomtemperature. After water quenching, the specimen is dried anddye-penetrated to investigate both open and closed cracks. For instance,Zyglo® water washable dye penetrants may be used. As the zirconiasamples are typically white or yellow, pink dye provides a vividdepiction of cracks and helps differentiate cracks from background orgrain boundaries. Methods for determining the cumulative or total cracklength per unit area in each specimen are known in the art and may bedetermined by scanning software electronically aggregating the lengthsof all cracks, backed up with visual confirmation by the technician. Theelectronic scanner resolution or magnification is generally notcritical, e.g., from as low as from 50× to as high as 1000×. The testerneed only be able to differentiate actual cracks from mere grainboundaries. As with any specified parameter, the value determined mustbe made over a sufficiently large region to provide a statisticallysound representation of the entire sample. The total crack length perunit area may be determined over such area by aggregating and averaginga number of smaller regions that collectively represent a statisticallysound region. A whole component may be studied or one or more regionsmay be evaluated. The studied or relevant region(s) or the wholecomponent may be considered a “component” for test purposes herein.

Utilizing propensity of cracks observed in a test specimen, the thermalshock resistance for a particular region or component may be normalizedand qualitatively scored, such as from 1 (the least resistance) to 5(the most resistance) as summarized hereunder:

-   -   1: Open cracks and many closed cracks.    -   2: Many closed cracks.    -   3: Some closed cracks.    -   4: Little closed cracks.    -   5: No cracks.

The appearance of various degrees of cracking in rapidly quenchedzirconia specimens or components and their corresponding qualitative,normalized thermal shock resistance (NTSR) value from 1 to 5 areillustrated in FIG. 2. A rating of 1 is least acceptable while a ratingof 5 is most acceptable. The herein disclosed inventive compositionswill typically produce a normalized NTSR rating of 3, 4, and 5. Toquantify propensity of cracks observed in a thermal shock resistancetest specimen, dye penetrated samples were optically scanned andsubjected to an image analysis computer software program. For example, atotal crack length per unit area of the test specimen may be measured byuse of commercially available image analysis software, e.g., ClemexVision PE, as reported in Table 1, and corresponding generally with theillustrative images of FIG. 2. (Other image analysis softwareapplications are also available to similarly measure the total cracklength of the specimen.)

TABLE 1 Illustrative examples of normalized thermal shock resistance(NTSR) index or rating, ranked from 1 to 5. NTSR Measured total cracklength Criteria of total crack Index per unit area (cm/cm²) length(cm/cm²) 1 81.2 >50 2 25.6 >20-≦50 3 16.5  >5-≦20 4 3.5 >1-≦5 5 0.01  ≦1

The stabilized refractory grade zirconia of this invention preferablydemonstrates a total crack length per unit area after quenching a testspecimen of the inventive material from 1100° C. into a water bath atroom temperature that is not greater than 5 cm/cm²; that is, itpreferably has a NTSR of at least 4. Still more preferably, thestabilized refractory grade zirconia of this invention demonstrates atotal crack length per unit area after quenching a test specimen of thestabilized refractory grade zirconia at 1100° C. into a water bath atroom temperature that is more preferably not greater than 1 cm/cm²; thatis, more preferably has a NTSR of 5. However, for some less demandingapplications, the inventive components may demonstrate crack lengths inexcess of 5 cm/cm², but preferably not greater than 20 cm/cm², thusdemonstrating a corresponding NTSR of 3 or higher. The intendedapplication determines the range of acceptable crack length. Thus,materials according to the present invention include those having athermal shock resistance rating of 4 or 5, as described herein.

As set forth in ASTM C 1525-04, thermal shock resistance can be assessedby measuring the reduction in flexural strength (MOR) produced by rapidquenching of test specimens heated across a range of temperatures. Forpurposes of the stabilized zirconia of this invention, regardingquantitative measurement of thermal shock resistance, a criticaltemperature interval may be determined by a reduction in the meanflexural strength of a determined amount, such as for example, at least30%. However, the test does not determine thermal stresses developed asa result of a steady state temperature differences within a ceramic bodyor of thermal expansion mismatch between joined bodies. Further, unlessthe test is repeated several times, the test is limited in its abilityto quantitatively determine the resistance of a ceramic material torepeated or cyclic shocks. Thus, it is preferred that the test berepeated to analyze the effect of cyclic temperature shocks, such as maybe experienced in a regenerative reactor.

Another key ceramic performance property with respect to the instantinvention is flexural strength, which can be measured by 3-point bendingtests as illustrated in ASTM F417. The test specimen, a small bar ofsquare cross section, rests on two cylindrical supports in a compressiontest machine. It is bent by the application of force, at mid-span, tothe opposite face of the bar from that resting on the two supports. Thebending force is applied by a third cylinder (identical to the othertwo) at a prescribed constant rate until the specimen breaks. Thebreaking rod, the dimensions of the specimen, and the test span are usedto calculate flexural strength.

As a ceramic material is heated, its density typically increases as aresult of pore shrinkage due to the sintering effect caused by the heat.Sintering may result in some of the ceramic crystals or componentstherein melting or undergoing other high temperature fusion orshrinkage, resulting in a slight decrease in bulk volume, but with anincrease in component strength. Thus, as a ceramic is heated, itsmodulus of rupture mechanical flexural strength (MOR) may typically alsocorrespondingly increase slightly. However, when the hot ceramic issubjected to relatively quick cooling, such as via water quenching,stress fractures may be introduced thereby causing a weakening orreduction in the mechanical flexural strength. The combination of themultimodal grains and the porosity remaining after sintering results ina lattice type structure that provides the improved strength, heatstress dissipation and handling characteristics, and cyclic thermalstress resilience. The preservative component prevents degradation ofthese desirable properties, thereby extending component life.

The claimed MOR and thermal shock property values refer to thoseproperty values determined after sintering, unless stated otherwise.ASTM 1505 describes the process for MOR determination. Limited durationexposure of the sintered component to annealing temperatures in excessof 1500° C., such as in excess of 1600° C. or at least 1800° C., mayfurther refine the component properties as described herein. Suchfurther thermal processing or annealing may generally further improvethe strength and thermal shock resistance of the inventive componentsand reactors as compared to such properties after original sintering.After such “annealing” of the sintered component, such as attemperatures in excess of commercial use temperature, such as at anexemplary temperature of at least 1800° C. for two hours, the formedceramic component according to this invention will demonstrates aretained porosity at ambient temperature in the range of from 5 to 45vol % based upon the formed volume of the component. Such componentsalso demonstrate a flexural strength (MOR) of at least 6 kpsi,preferably at least 10 kpsi, and provide a thermal shock resistancerating of at least four (4), preferably at least five (5). The MORflexural strength of the zirconia ceramic used for materials and reactorcomponents according to this invention should be greater than or equalto about 6 kpsi (41.3 MPa) after initial sintering to at least 1500° C.and subsequent quenching to ambient temperature. Also, the MOR ispreferably greater than or equal to about 6 kpsi (41.3 MPa) when thesintered component is further thermally conditioned, such as byreheating and quenching (e.g., annealed) to operating conditions. Forexample, the thermal conditioning may entail reheating the component toa temperature in a range such as from 1500° C. to 1800° C. or perhapseven up to 2000° C. Surprisingly, many of the inventive componentsroutinely demonstrate a MOR of at least 6 kpsi (41.3 MPa) after furtherthermal processing. The combination of a normalized thermal shockresistance rating of 4, with such MOR strength is recognized herein as aminimal MOR and shock resistance properties that are necessary acrossthe required broad reactor temperature spectrum to provide for long-termcommercial utilization of high temperature pyrolysis chemistryprocesses, over a desired life cycle of the reactor component. Thepreservative component of this invention functions to prolong theseproperties of the component within that range of acceptability,correspondingly extending the useful life of the component and process.If desired, the effect of long duration MOR changes may also beevaluated to determine commercial suitability, such as the MOR after,say for example, one month of cyclic processing (annealing). Thecomponents and apparatus of the subject invention, however, are expectedto provide life duration for the relevant components and apparatusbeyond the level that was previously available in the art.

In one aspect, this invention includes a refractory material, suchmaterial having application in one aspect for use with a regenerativethermal pyrolysis reactor apparatus, such as for components useful forpyrolyzing a hydrocarbon feedstock (e.g., petroleum liquids, gas, orcoal). In other aspects, this invention may be utilized for pyrolyzingor otherwise thermally processing various feedstocks other thanhydrocarbon feeds at high temperature, such as but not limited to otherhigh temperature chemical processes, reactions, such as but not limitedto using various oxidizable, flammable, combustible, or otherwisethermally reactive materials, whether solid, liquid, or gas. Althoughthe inventive materials are useful at high temperatures (>1500° C.),they may also be useful in various lower temperature applications. Theterm “hydrocarbon feedstock” as used herein is defined broadly toinclude virtually any hydrocarbonaceous feed and may also includesubstantially carbonaceous feeds such as graphite or coke. Exemplaryhydrocarbon pyrolysis feedstocks that may have particular applicabilityfor use in the present invention typically comprises but are not limitedto one or more hydrocarbons such as methane, ethane, propane, butane,naphthas, gas oils, condensates, kerosene, heating oil, diesel,hydrocrackate, Fischer-Tropsch liquids, alcohols, distillate, aromatics,heavy gas oil, steam cracked gas oil and residues, crude oil, crude oilfractions, atmospheric pipestill bottoms, vacuum pipestill streamsincluding bottoms, heavy non-virgin hydrocarbon streams from refineries,vacuum gas oils, low sulfur waxy residue, heavy waxes, coal, graphite,coke, tar, atmospheric residue, heavy residue hydrocarbon feeds, andcombinations thereof. Undesirable fractions, solids and non-volatilescontained in the feedstreams may optionally be removed by one or moreseparation techniques, prior to feeding a volatizable fraction into thereactor. Diluents or other additives, such as but not limited to steam,water, methane, and hydrogen, may also be included within thefeedstreams.

This invention includes but is not limited to use of components,apparatus, reactors, and methods disclosed in various, previous patentapplications, the entirety of each of which are included herein byreference, including (i) U.S. application Ser. No. 60/753,961, filedDec. 23, 2005, titled “Controlled Combustion for Regenerative Reactors,”(ii) U.S. application Ser. No. 11/639,691, filed Dec. 15, 2006, titled“Controlled Combustion for Regenerative Reactors;” (iii) U.S.application Ser. No. 11/643,541, filed Dec. 21, 2006, titled “MethaneConversion to Higher Hydrocarbons;” and (iv) U.S. patent applicationSer. No. 12/119,762, filed May 13, 2008, titled “Pyrolysis ReactorConversion of Hydrocarbon Feedstocks Into Higher Value Hydrocarbons.”These patent applications teach and disclose various apparatus andmethods for pyrolyzing hydrocarbon feeds in reverse flow regenerativepyrolysis reactors, including deferred combustion and controlled heatpositioning processes. The inventions disclosed in this presentinvention may be suitable for use with but not limited to reactors asdisclosed in these previous applications. In some embodiments, theinventive components and reactors may comprise reverse flow regenerativepyrolysis reactor systems, including but not limited such systems thatmay utilize deferred combustion in a reverse flow reactor to heat thereactor core. The inventive components provide the strength, thermalshock resistance, and chemical stability required to enablecommercialization of such apparatus and processes to operate attemperatures of at least 1500° C., and even in some embodiments inexcess of 1600° C., in still other embodiments in excess of at least1700° C., and in even other embodiments at temperatures in excess of2000° C. The inventive components, apparatus, and process provides for alarge-scale, cyclic, reverse-flow reactor system that is useful andoperable on a commercially desirable scale and life cycle.

Grain size or particle size, refers to the diameter or geometric size ofindividual grains of the matrix comprising a multimodal graindistribution. Grains are distinct from crystallites and from the variouscrystals that constitute a particle or grain, although a grain may becomprised of a single crystal. A single grain can comprise one orseveral crystallites. A crystallite can comprise one or severalcrystals, a crystal being a solid-state matter that has uniformstructure. A grain or particle is the individual ceramic or stabilizergranular material that forms the solid matrix for the ceramic component.The grains or particles are sintered and bonded together at grainboundaries to create a formed ceramic component. Dynamic lightscattering and laser light diffraction analysis using a unified scattertechnique (Microtrac® 3500) can be used to determine average particlesize and particle size distribution. Microtrac® instruments can measureparticle size ranging from 0.024 to 2800 μm and provide goodinstrument-to-instrument agreement, sample-to-sample agreement,instrument internal repeatability and particle distribution breadth.

The “D50” or average particle size measured by a laser light diffractionmethod is one type of average particle size represented as D50 or meandiameter. The D50 average particle size is a value determined by using aparticle size distribution measuring device and represents a particlesample cut diameter which is the 50% volume or weight fraction valueafter determining the minimum and maximum sizes contributing to theintegrated volume of a specific peak of a particle size distribution.Similarly D90, D10, D99 respectively corresponds to the 90, 10 and 99%volume or weight fractions of the particle size distribution. Theaverage (D50) or any other particle size cut value can be determined bymicroscopy methods such as optical microscopy (OM), scanning electronmicroscopy (SEM) and transmission electron microscopy (TEM). The averageparticle size values measured by microscopy methods also can beconverted to D50 values by methods known in the field. The particle sizedistribution of the first grains alternatively can be determined by asieve and mesh classification method as known in the art.

In some embodiments, the inventive materials, components, and reactorsystems may include a first grain mode zirconia ceramic compositionhaving a D50 grain size in the range of from 0.01 μm up to 2000 μm,while in other embodiments the reactor system may include a first grainmode zirconia ceramic composition having a D50 grain size in the rangeof from 5 μm to 800 μm. The size preference may be determined by theparticular component being prepared. For example, larger, bulkiercomponents such as structurally demanding components may utilize grainsized within the broader range, while more intricate or delicatecomponents such as thin-walled honeycomb monoliths might benefit fromsmaller grain sizes within the latter range.

The composition includes at least a first grain mode comprising astabilized zirconia ceramic that is stabilized with a matrix oxidestabilizer and a second grain mode. The composition also includes apreservative component. In many embodiments, the first grain modecomprises partially stabilized zirconia. In many embodiments, thepartially stabilized first grain mode zirconia may be stabilized byyttria or an yttria containing compound, such as but not limited toyttria oxide. In other embodiments, the stabilizer may be anotherstabilizer, such as Mg, Ca, Ce, MgO, CaO, Y₂O₃, CeO₂, or mixturesthereof.

In many embodiments, the second grain mode comprises stabilized ceramic,preferably a stabilized zirconia, and preferably a fully stabilizedzirconia. The stabilized second grain mode ceramic includes a secondgrain mode stabilizer, such as Y, Mg, Ca, Ce, MgO, CaO, Y₂O₃, CeO₂, ormixtures thereof The preservative component may comprise either amaterial separate from the second grain stabilizer, or may be comprisedof the second grain stabilizer, particularly an excess amount of thesecond grain stabilizer beyond that amount that is engaged instabilizing the second grain mode stabilized ceramic. In otherembodiments, the second grain mode may consist essentially of thepreservative component, wherein such preservative component comprises astabilizing material, such as yttria, Mg, Ca, Ce, MgO, CaO, Y₂O₃, CeO₂,or mixtures thereof In many embodiments, the preservative componentcomprises or consists of the same materials that are used to stabilizethe first grain ceramic. In many such embodiments the first grain matrixoxide stabilizer and preservative component include yttria, either neator as part of a compound, while others may include MgO, CaO, Y₂O₃, CeO₂,or mixtures thereof.

In many embodiments, the material comprises a ceramic grain distributionincluding partially stabilized zirconia in at least the first mode butalso possibly a partially stabilized or fully stabilized zirconia in thesecond mode. In some embodiments, the second grain mode comprises atleast 14 wt. % of a preservative component (fully stabilized), orsometimes at least 15 wt. %, 20 wt. %, 30 wt %, 50 wt. %, 80 wt. %, 90wt. %, 95 wt. %, 99 wt. % or in some embodiments the second grain modemay consist essentially of preservative component, based upon the weightof the second grain mode.

The combination of enhanced packing density due to the multimodal natureof the structure, plus the porosity, plus preservative componentuniquely provides an improved combination of MOR flexural strength,thermal shock resistance, and component life expectancy that was notpreviously known in the industry. The inventive composition comprises amultimodal grain distribution suitably designed for close packing andcorresponding high density, while at the same time providing a welldistributed porosity throughout the packed matrix. The multimodal graindistribution facilitates closely packing the component grains whichprovides density and commensurate MOR strength. However, the multimodaldistribution according to this invention provides at least a minimumamount of matrix porosity, such as at least 5 vol % and preferably atleast 10 vol %, up to 45 vol % porosity, or in some embodiments up to 30vol %, based upon the bulk volume of the inventive material. Theporosity feature of the matrix facilitates small scale matrixflexibility among the matrix particles while also permitting dissipationof both mechanical and thermal stress concentrations (particularly withrespect to arresting crack propagation). The porosity also provides highsurface area for improved heat absorption and dissipation, as comparedto typically less-porous, high-density, high-strength ceramics such asother refractory and engineering grade ceramics. The porosity feature isattributed with providing improved thermal stress crack resistance byinhibiting crack formation and arresting crack propagation, andsimultaneously facilitating some elastic deformation of the matrixstructure, thereby providing enhanced service life in the stressful,high temperature, cyclic thermal applications. The porosity of theceramic matrix of the formed ceramic component is measured at ambienttemperature, such as at 20° C., after sintering for at least ten minutesat 1500° C., (and also even after two hours of further annealing attemperatures above 1500° C., such as up to 1800° C. or even up to 2000°C.) is in the range of from 5 to 45 vol %, or sometimes in the range offrom 10 to 30 vol %, based on the bulk volume of the formed ceramiccomponent. The porosity created in or among the closely packed grains ispreferably substantially uniformly dispersed throughout the composition.

In addition to improved density, the close grain packing alsofacilitates enhanced sintering among the coarse grits as compared tosintering of only a narrow grain size embodiment. The limitations onratio of second grit mode grain size versus size of the first or coarsegrit mode particles provide a range of formed ceramic componentproperties that may be preferred for use in certain components orreactors useful for commercial scale applications for performing hightemperature thermal or pyrolysis processes. Second grit mode particlesfit within the interspatial gaps, adjacent the tangent point betweencoarse grits and provide close packing and corresponding high packingdensity. Second grits at or near the tangent between coarse grits mayalso enhance bonding after sintering the multimodal mix. The resultingadherent bonding between coarse grits is also at least partlyresponsible for the corresponding high density and improved flexuralstrength of the ceramic composition. A desired porosity value with theabove range may be application-defined and may be facilitated duringmanufacture or preparation of the formed ceramic composition such as bycontrolling certain manufacturing or preparation properties, such as butnot limited to grain size selections and ratios of amount of coarseversus second grains, mixing energy and methods, extrusion or pressingforces applied to the component during formation, sintering temperatureand time, etc. For example, preparation of the formed ceramic componentprior to sintering may utilize a lower extrusion pressure or compactionpressure than is traditionally utilized in manufacture of engineeringgrade or even some refractory grade ceramics, whereby grain compactionis controlled to avoid over-compaction. Preparation method may beadjusted as needed to yield a formed ceramic component or reactor thatincludes the desired porosity.

The particles comprising the multimodal grain distribution can besubstantially any shape. In many embodiments, a preferred shape may bethose particle shapes that are substantially spherical or more sphericalin dimensions than nonspherical. Some non-limiting acceptable examplesinclude spherical, ellipsoidal, polyhedral, distorted spherical,distorted ellipsoidal, distorted polyhedral shaped, angular,rectangular, tetrahedral, quadrilateral, elongated, etc. The shape ofsecond grain particles may generally be of less importance than theshape of first grain particles. Spherical first grain is particularlybeneficial in providing close packing, density, optimum porosity, andflowability during powder processing and fabrication. A preferredspherical shape of the first grain can be characterized by an aspectratio less of than 2.5, or preferably less than 2.0, or more preferablyless than 1.5. Grains with generally smoother surfaces may also bepreferred as compared to grains having highly irregular surface shapes.

Spherical shape refers to a symmetrical geometrical object where the setof all points in three dimensional space (R³) which are at the distanceR from a fixed point of that space, where R is a positive real numbercalled the radius of the sphere. The aspect ratio of a shape is theratio of its longest axis to its shortest axis. The aspect ratio ofsymmetrical objects may also be described by the ratio of two measures(e.g. length and diameter). The aspect ratio can be measured bymicroscopy methods such as optical microscopy (OM), scanning electronmicroscopy (SEM), and transmission electron microscopy (TEM), incombination with image analysis software, wherein a two-dimensionalshape is projected.

The particles or grains can be either single crystalline orpolycrystalline. Polycrystalline grain is made of many smallercrystallites with varying orientation. Various types of grains can beutilized which include but are not limited to agglomerated and sintered,fused and crushed, and spherodized. In one form, the grains areagglomerated and sintered powder which is produced by spray drying of asuspension consisting of fine powders and organic binder and subsequentsintering. In another form, the grains are fused and crushed, which isproduced by fusing in arc furnaces and crushing of the cold block. Instill another form of the disclosure, the grains are spherodized, suchas by atomization of agglomerates using a plasma flames to fabricatesubstantially spherical shaped particles.

The superior thermal shock resistance, relative chemical inertness,preserved crystalline structure, improved flexural strength, and hightemperature capability of the inventive compositions, components, andreactors of the present invention provide crystalline stability andstructurally soundness under cyclical thermal conditions at temperaturesof 1500° C. and higher, such as up to 1700° C., 1800° C., or in someembodiments, up to 2000° C., particularly as compared to prior artrefractory and thermal components and reactors. Such attributes andproperties may facilitate components and reactors that can replaceconventional refractories and also facilitate use of processes inrelatively large scale commercial applications that were previously noteconomical or technically achievable. In particular, the heat stable,formed ceramic components, reactors, and processes may find particularapplication in refining, petrochemical, chemical processing, and otherhigh temperature thermal applications. It is believed that the improvedcombination of properties provided according to the present disclosuremay facilitate commercial service periods of greater than 1 year, forexample even up to about 10 years in some applications.

In one form, the inventive material and components may be prepared bymanufacturing techniques such as but not limited to conventional ceramicpowder processing techniques, e.g., mixing, milling, pressing orextruding, sintering and cooling, employing as starting materials asuitable ceramic powder and a binder powder in the required volumeratio. Certain process steps may be controlled or adjusted to facilitatemanufacture of the desired porosity range and performance properties.For example, the two or more modes of powders, oxides, preservatives,and/or stabilizers may be milled in a ball mill in the presence of anorganic liquid such as ethanol or heptane for a time sufficient tosubstantially disperse the powders in each other. Excessive binderpowder and liquids may be removed and the milled powder dried, placed ina die or form, pressed, extruded, formed, caste or otherwise formed intoa desired shape. The resulting “green body” is then sintered attemperatures of at least 1500° C. and commonly up to about 1800° C. forat least ten minutes, and often for times typically ranging from about10 minutes to about two hours and in some applications even up to 4hours. The sintering operation may be performed in an oxidizingatmosphere or inert atmosphere, and at ambient pressure or under vacuum.For example, the oxidizing atmosphere could be air or oxygen, the inertatmosphere could be argon, and a reducing atmosphere could be hydrogen.The sintering atmosphere, temperature, and kiln environment may alsointroduce secondary oxides (as discussed previously herein) into thecomponent, either desirably or undesirably, as a contaminant ordesired/permitted constituent of the ceramic component. Thereafter, thesintered body is allowed to cool, typically to ambient conditions. Thecooling rate may also be controlled to provide a desired set of crystalsizes and performance properties in the particular component.

More particularly, the advantageous properties and/or characteristics ofthe multimodal ceramics are realized in part from the close packing ofthe ceramic grains, wherein one mode of a bimodal grain distributionincludes a D50 first grain particle size in the range of from 5 to 2000μm, or from 5 to 800 μm; and the second grain mode of graindistribution, including the preservative component, includes a D50particle size in the range of from at least about 0.01 μm to not largerthan one-fourth (¼) of the D50 grain size of the first grain. The secondgrains are substantially evenly disbursed within the first grains.According to the present invention, the size of the preservativecomponent particles is in some embodiments consistent with the sizelimitations for the other particle size limitations and rangespertaining to the second grain mode. In one embodiment, for example, thesecond grains may include a D50 size value that ranges from 0.01 to 100μm. In other embodiments, for example, the fine mode grains may includea D50 size value that ranges from 0.05 to 44 μm, while in still otherembodiments the fine mode grains include a D50 size value that rangesfrom 0.05 to 5 μm. For example, in one embodiment, the first grain modeincludes a D50 size that ranges from 20 to 200 μm, while thecorresponding second grain mode may range from 0.05 to 5.0 μm. In stillother embodiments, the second grain mode may include a D50 average sizediameter not greater than one-eight the D50 size of the correspondingfirst grain mode. In some embodiments the D50 size of the fine modegrains may not exceed one tenth the D50 size of the first mode grains(e.g., not larger than one order of magnitude smaller than the firstgrain mode), while in other embodiments the D50 size of the second grainmode will generally be less than about two orders of magnitude smallerthan the D50 size of the first grain mode (e.g., the second grains aresometimes not larger than about 100 times smaller than the D50 diameterof the first grains.) In other embodiments, the size of the preservativecomponent particles may be consistent with the size of the first modeparticles or have a size distribution relatively distinct from the sizeof either or both of the first and second modes.

In one non-limiting exemplary form, a grain distribution of partiallystabilized zirconia particles with a first grain size distribution of 21to 65 μm and a second grain size distribution of 0.05 to 2 μm and areutilized. In still yet another exemplary embodiment, a bimodaldistribution of stabilized zirconia particles with a first grain sizedistribution of 30 to 120 μm and a second grain size distribution of 0.1to 5 μm are utilized. In still yet another exemplary form, a bimodaldistribution of stabilized zirconia particles with a first grain sizedistribution of 40 to 200 μm and a second grain size distribution of 0.1 to 10 μm are utilized. In yet another exemplary form, a distributionof stabilized zirconia particles with a first grain distribution of 100to 500 μm and a second grain distribution of 1 to 20 μm are utilized.

For example, for various embodiments the D50 lower limit of the secondgrain stabilized zirconia may be 0.01 or 0.05 or 0.5 or 1 or 5 μm indiameter. A practical D50 lower limit on the second grain stabilizedzirconia grains for many embodiments may be about 0.1 μm. Grains smallerthan 0.1 m may tend to be of limited usefulness in many applications dueto the fact that such small grains may not distribute evenly and tend tomelt together and combine into sintered grains that are of about thesame size as do grains that are at least 0.1 μm. The stabilized zirconiaand stabilizer grains that are of at least about 0. 1 μm in diametertypically do not change size during or after sintering, whereas thenanoparticles may tend to combine into larger particles. For at leastthese reasons, the second grain mode of many embodiments of the subjectinvention might not include nanoparticle D50 size grit, unless such modeis purposefully introduced into and mixed with the coarse and secondgrain modes as a third or other mode, or as a secondary oxide. Commonly,nanoparticle modes of zirconia or stabilizer may generally only beconsidered as the second grain mode of the multimode structure when suchgrains are of sufficient presence to combine with each other to providea second grain mode after sintering that provides mode grains of atleast 0.01 μm after sintering and more preferably at least 0.1 μm aftersintering. The D50 upper limit of the second grain mode, including thepreservative component particles, may be 100 or 44 or 20 or 15 or 10 or5 or 1 μm in diameter. The D50 lower limit of the first grain stabilizedzirconia may be 5 or 20 or 25 or 30 or 40 or 100 μm in diameter. The D50upper limit of the first grain stabilized zirconia may be 800 or 500 or200 or 100 or 50 μm in diameter. The lower size limitation however, forthe second grain mode, including the limitation for the preservativecomponent particles therein, is consistent with size limitations for theother particle size limitations and ranges pertaining to the secondgrain mode and is a D50 diameter of at least 0.01 μm, and sometimespreferably at least 0.1 μm.

In still yet another exemplary form, the D50 average particle size ofthe first grains may be about 30 μm and the D50 average particle size ofthe second grains is about 0.3 μm. In another non-limiting exemplaryform, the D50 average particle size of the first grains is about 50 μmand the D50 average particle size of the second grains is about 0.5 μm.In yet another non-limiting exemplary form, the D50 average particlesize of the first grains is about 100 μm and the average particle sizeof the second grains is about 1.0 μm. In yet another non-limitingexemplary form, the D50 average particle size of the first grains isabout 500 μm and the D50 average particle size of the second grains isabout 5.0 μm.

A non-limiting example of a multimodal (bimodal) grain distribution mayinclude from 1 to 20 wt. % of second grain particles and 80 to 99 wt. %of first grain particles. Another non-limiting example is a graindistribution that includes from 1 to 50 wt. % of second grain particlesand 50 to 99 wt. % of first grain particles. Yet another non-limitingexample is a grain distribution that includes from 1 to 80 wt. % ofsecond grain particles and 20 to 99 wt. % of first grain particles Stillanother suitable, non-limiting example of a bimodal grain distributionincludes 20 to 30 wt. % of first grains, such as but not limited to aD50 particle size of 30 μm, and 70 to 80 wt. % of second grains, such asbut not limited to a D50 particle size of 0.3 μm. Another suitable,non-limiting example of a bimodal grain distribution includes 30 to 40wt. % of first grains, such as but not limited to a D50 particle size of30 μm, and 60 to 70 wt. % of second grains, such as but not limited to aD50 particle size of 0.3 μm. Another suitable, non-limiting example of abimodal grain distribution includes 50 to 70 wt. % of first grains, suchas but not limited to a D50 particle size of 30 μm, and 30 to 50 wt. %of second grains, such as but not limited to a D50 particle size of 0.3μm. Another suitable, non-limiting example of a bimodal graindistribution includes 85 to 99 wt. % of first grains, such as but notlimited to a D50 particle size of 30 μm, and 1 to 15 wt. % of secondgrains, such as but not limited to a D50 particle size of 0.3 μm. Yetanother suitable, non-limiting example of a bimodal grain distributionincludes 94 to 99 wt. % of first grains, such as but not limited to aD50 particle size of 30 μm, and 1 to 6 wt. % of second grains, such asbut not limited to a D50 particle size of 0.3 μm.

Another non-limiting example of an exemplary, generally bimodal graindistribution includes 20 wt. % first grain with a D50 particle size of40 μm, and 80 wt. % second grain particles with a D50 particle size of1.0 μm. Another non-limiting example of an exemplary bimodal graindistribution includes 50 wt. % first grain with a D50 particle size of40 μm, and 50 wt. % second grain particles with a D50 particle size of0.4 μm. Another non-limiting example of an exemplary bimodal graindistribution includes 88 wt. % first grain with a D50 average particlesize of 50 μm, and 12 wt. % second grain particles with a D50 averageparticle size of 0.5 μm. Still another non-limiting example of a bimodalgrit includes 85 wt. % of first grain with an average particle size of100 μm, and 15 wt. % of second grain with an average particle size of1.0 μm. The wt. % of the second grain size distribution may be, forexample, from 1 to 80 wt. % or 1 to 50% wt. % or 1 to 20 % or 2 to 15%with the remaining grains constituting the coarse grit or other modesize distributions such as larger, smaller, or intermediatedistributions. Such exemplary grain size distributions may provide auseful density and porosity combination suitable for various pyrolysisapplications.

In one embodiment, the invention includes a refractory materialcomprising: (i) at least 20 wt. % of a first grain mode, the first grainmode comprising a stabilized zirconia having a D50 grain size in therange of from 5 to 800 μm based upon the total weight of the refractorymaterial, the stabilized zirconia including a matrix oxide stabilizer;(ii) at least 1 wt. % of a second grain mode having a D50 grain size inthe range of from 0.01 μm up to not greater than one-fourth the D50grain size of the first grain mode stabilized zirconia, based upon thetotal weight of the refractory material; and (iii) at least 1 wt. % of apreservative component (with respect to the total weight of the materialor component); wherein after sintering the material has porositymeasured at 20° C. (e.g., room or ambient temperature) in the range offrom 5 to 45 vol %. The preservative component may be included within(that is, associated with by virtue of grain size) the first mode,second mode, and/or as a separate mode. The “at least 1 wt. %” minimumthreshold determination is made by aggregating the sum of allpreservative component present within the material and does not requirethat any specific mode include at least 1 wt. %. This includes not onlythe separately distinguishable preservative component material that ispresent in one or more modes to function as the preservative component,but also the portion of stabilizer that is present within a mode that isin excess of the amount of such stabilizer that is functioning toprovide at least partial crystal stabilization within a mode. Althoughdetermination of the latter may be difficult to accurately orconsistently assess or define, it is deemed that a fully stabilized modeor a substantially fully stabilized mode contains sufficient stabilizeracting as preservative component such that it meets the “at least 1 wt.%” minimum threshold.

In other embodiments, the inventive material comprises at least 10 wt. %of combined weight of the preservative component, the matrix oxidestabilizer, and optionally a second grain mode stabilizer, based uponthe total weight of the refractory material. In still other embodiments,all three of the preservative component, the matrix oxide stabilizer,and optional second grain mode stabilizer will each include or consistessentially of the same stabilizer material, such as but not limited toan yttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixturesthereof.

In other embodiments, the second grain mode comprises a fully stabilizedzirconia, the fully stabilized zirconia being stabilized by at least 14wt. % of a second grain zirconia stabilizer based upon the weight of thesecond grain stabilized zirconia. As discussed above, at least a portionof the at least 14 wt. % functions to stabilize the crystal structurewhile at least another portion is acting as the claimed minimum of “atleast 1 wt. %” of preservative component to offset the progressive lossof stabilizer from the first mode stabilized zirconia. Yttria is one ofthe most active stabilizers and generally has the lowest weight fractionrequirement (e.g., 14 wt. % or 8 mole % yttria) among the stabilizercomponent candidates to render a zirconium fully stabilized. As fordefining this aspect of the invention, this same 14 wt. % limit isapplied to all other stabilizer candidate materials other than yttriaand is also deemed by definition to meet the “at least 1 wt. %” minimumamount of preservative component present.

In some embodiments, the second grain mode comprises both thepreservative component and a stabilized zirconia. Often, each of thepreservative component and the second grain zirconia stabilizercomprises substantially the same compounds as comprise the first grainmatrix oxide stabilizer. For embodiments that comprise a fullystabilized zirconia in the second grain mode, the second grain fullystabilized zirconia is stabilized by a second grain mode zirconiastabilizer.

In many embodiments, the second grain mode comprises at least 15 wt. %of combined weight of second grain mode stabilizer and preservativecomponent, based upon the weight of the second grain mode. Such minimumaggregated amount obviates the need to rigorously distinguish betweenthe amount of stabilizer acting to stabilize the crystal structure andthe excess amount available to support the progressive loss ofstabilizer from within the first grain mode. In other embodiments, therefractory material comprises at least 20 wt. % of combined weight ofthe first grain mode matrix oxide stabilizer, second grain modestabilizer and preservative component, based upon the total weight ofthe material. In other aspects, the aggregate weight of the matrix oxidestabilizer, the preservative component, and an optional second grainmode stabilizer comprises at least 10 wt. %, and sometimes at least 15wt. % of the weight of the material, based upon the total weight of thematerial. In some embodiments, the preservative component is providedwithin at least two of the first grain mode, the second grain mode, andan optional another grain mode. In another aspect, the preservativecomponent may be provided substantially within only the second grainmode.

In other versions, the invention includes a stabilized refractoryceramic component that is suitable for use with a pyrolysis reactor, thecomponent including; (i) at least 20 wt. % of first grain mode, thefirst grain mode including stabilized zirconia having a grain size inthe range of from 5 to 800 μm based upon the total weight of thecomponent, the stabilized zirconia including a matrix oxide stabilizerto stabilize the first grain mode stabilized zirconia; and (ii) at least1 wt. % of a second grain mode having a D50 grain size in the range offrom 0.01 μm up to not greater than one-fourth the D50 grain size of thefirst grain mode, dispersed within the first grain mode, based upon thetotal weight of the refractory ceramic component, the second grain modecomprising at least 1 wt. % of a preservative component based upon theweight of the second grain mode, to stabilize the first grain modestabilized zirconia; wherein after sintering, the component has porosityat ambient temperature in the range of from 5 to 45 vol. %, based on thevolume of the component. In such embodiments, the preservative componentmay be provided as a component of a stabilized ceramic compound withinthe second grain mode, such as a stabilized zirconia. In some of suchaspects, the stabilized zirconia may comprise a fully stabilizedzirconia, wherein the fully stabilized zirconia is stabilized by atleast 10 wt. %, preferably at least 14 wt. % (e.g., fully stabilized) ofa second grain zirconia stabilizer based upon the weight of the secondgrain stabilized zirconia. In some of such embodiments, at least aportion of the second grain zirconia stabilizer functions as thepreservative component and preferably but not necessarily, the secondgrain zirconia stabilizer, the first mode stabilizer, and thepreservative component comprise substantially the same compounds.

In still other embodiments the second grain zirconia stabilizer includesa stabilizer other than the first grain matrix oxide mode stabilizer andthe second grain mode further comprises separately, a preservativecomponent that is also preferably substantially the same compound ascomprises the first grain mode matrix oxide stabilizer. In someembodiments, the second grain mode comprises at least 14 wt. %, 15 wt.%, 20 wt. %, or 50 wt. % of combined weight of stabilizer andpreservative component, based upon the weight of the second grain mode,while in still other embodiments, the second grain mode comprises atleast 80 wt. %, or 90 wt. %, or 95 wt. % of preservative component,based upon the weight of the second grain mode. In still otherembodiments, the second grain mode may consist essentially ofpreservative component.

The second grain mode comprises at least 1 wt. % of preservativecomponent, or at least 5 wt. %, 10 wt. %, 15 wt. %, 20 wt. %, 50 wt. %,80 wt. %, 90 wt.%, or substantially 100 wt. % preservative component,based upon the weight of the second grain mode. The preservativecomponent includes that amount of stabilizer that is in excess of thestabilizer that is engaged in stabilizing the crystal structure of therespective mode in which such component is located. The amount ofpreservative component is that amount of stabilizer present that is inaddition to the stabilizer (if any) that is employed stabilizing thesecond grain zirconia if present. When the second grain zirconia ispresent, typically the second grain zirconia is stabilized by at least10 wt. % of second grain matrix stabilizer and more typically at least14 wt. % as required to achieve a fully stabilized zirconia. Thepreservative component portion thereby includes that portion ofstabilizer that is additional to the amount (typically at least 14 wt.%, but may be other greater percentages) utilized in stabilizing thesecond grain zirconia matrix. Consequently, in some embodiments, thesecond grain mode may comprise at least 5 wt. % of stabilizer material(partially stabilized second grain mode embodiments) and at least 1 wt.% of preservative component, the 1 wt. % preservative component eitherin form of a distinct additional material or additive with respect tothe 5 wt. % of second grain stabilizer material or an additional portionof the stabilizer material that is incremental to the 5 wt. % of secondgrain stabilizer material (for example, a portion of stabilizer materialover 5 wt. % stabilizer within a fully stabilized zirconia). In otherembodiments, the second grain mode comprises at least 10 wt. % (at leastpartially stabilized), 14 wt. % (fully stabilized, wherein at least aportion of the stabilizer functioning as the preservative component), 15wt. %, or at least 20 wt. % of combined weight of stabilizer andpreservative component, based upon weight of the second grain mode.

According to some other embodiments of invention, the first grain modecomprises at least 20 wt. % of the total weight of the refractorymaterial, based upon the total weight of the refractory material. Insome embodiments, the first grain mode comprises at least 50 wt. % ofthe multimodal grain distribution, based upon the total weight of themultimodal grain distribution. In other embodiments, the first grainmode comprises up to 99 wt. % of the total weight of the multimodalgrain distribution, based upon the total weight of the multimodal graindistribution.

In some aspects, the inventive distribution may comprise from 1 to 20wt. % of second grain mode and from 80 to 99 wt. % of first grain mode,based upon the total weight of the multimodal grain distribution. Inother aspects, the inventive multimodal distribution may comprise from 1to 50 wt. % of the second grain mode and from 50 to 99 wt. % of thefirst grain mode, based upon the total weight of the multimodal graindistribution. Still other embodiments may include from 1 to 80 wt. % ofthe second grain mode and from 20 to 99 wt. % of the first grain mode,based upon the total weight of the multimodal grain distribution.

In some embodiments, the first grain mode stabilized zirconia comprisesat least 6 wt. % of matrix oxide stabilizer (e.g., at least partiallystabilized), or sometimes at least 14 wt. % of matrix oxide stabilizer(e.g., fully stabilized by yttria), the matrix oxide stabilizercomprising at least one of an yttrium-containing compound, CaO, MgO,Y₂O₃, CeO₂, and mixtures thereof, based upon the weight of the firstgrain stabilized zirconia. Often, the matrix oxide stabilizer comprisesan oxide-based compound and is thus named as an “oxide stabilizer,” butas used herein the term “oxide stabilizer” shall be defined more broadlyto also include non-oxide based compounds and elements, such as but notlimited to non-oxide based yttrium-containing compounds, calcium,magnesium, cesium, and the like. However, the second grain modepreferably comprises at least 14 wt. % of at least one of anyttria-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof,based upon the weight of the second grain mode.

In certain embodiments, the refractory material includes; (i) 20 to 50wt. % of the first grain mode, based upon the total weight of thematerial; (ii) 1 to 80 wt. % of the second grain mode, based upon thetotal weight of the material; and (iii) a combined total of at least 1wt. % of the preservative component within at least one of the firstgrain mode, the second grain mode, and the optional another grain mode.

In addition to a refractory material, the present inventions alsoinclude a stabilized ceramic refractory component that is suitable foruse with a pyrolysis reactor, the component comprising; (i) at least 20wt. % of a first grain mode based upon the total weight of therefractory component, the first grain mode including stabilized zirconiahaving a D50 grain size in the range of from 5 to 800 μm, the stabilizedzirconia including a matrix oxide stabilizer to stabilize the firstgrain mode stabilized zirconia; (ii) at least 1 wt. % of a second grainmode having a D50 grain size in the range of from 0.01 μm up to notgreater than one-fourth the D50 grain size of the first grain mode,dispersed within the first grain mode, based upon the total weight ofthe refractory component; and (iii) at least 1 wt. % of a preservativecomponent dispersed within the aggregate of at least one of (a) thefirst grain mode stabilized zirconia, (b) the second grain mode, and (c)an optional another grain mode, based upon the total weight of therefractory component; wherein the component has porosity at 20° C. inthe range of from 5 to 45 vol %. In many embodiments the componentcomprises at least 10 wt. % of combined weight of the preservativecomponent, the matrix oxide stabilizer, and optionally a second grainmode stabilizer, based upon the total weight of the component.

Often, the second grain mode consists of the preservative component. Inother embodiments, the second grain mode consists essentially of thepreservative component. The claimed limitation of a second grain modeand claimed limitations of a preservative component may in someembodiments be the same functional components, merely defined by twodistinct sets of limitations. That is, in some embodiments, such asthose that do not include a stabilized zirconia within the second grainmode, the second grain mode may include or be comprised of substantiallyexclusively the preservative component. Thereby, the at least 1 wt. % ofsecond grain mode and the at least 1 wt. % of preservative component aresubstantially the same granular portions of the material, namely, thesmaller or more fine granular material. The invention does not alwaysrequire that the second grain mode be a physically distinct andadditional material or element from the preservative component, thoughin many embodiments they will be two separate, physically distinctmaterials.

In many embodiments, component comprises a flexural strength of at least6 kpsi and a normalized thermal shock resistance rating of at leastfour. The first grain mode stabilized zirconia comprises at least 1 wt.% of matrix oxide stabilizer, the matrix oxide stabilizer comprising atleast one of an yttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, andmixtures thereof, based upon the weight of the first grain stabilizedzirconia. The first grain mode stabilized zirconia preferably maycomprise at least 6 wt. % of the matrix oxide stabilizer (e.g., at leastpartially stabilized). The preservative component comprises at least oneof an yttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixturesthereof.

In another aspect, the inventions include a method of preparing aceramic composition comprising the steps of: a) preparing a granularceramic composition or mixture including at least: (i) at least 20 wt. %of a first grain mode based upon the total weight of the ceramiccomposition, the first grain mode comprising stabilized zirconia havinga D50 grain size in the range of from 5 to 800 μm, the stabilizedzirconia including a matrix oxide stabilizer; and (ii) at least 1 wt. %of a second grain mode having a D50 grain size in the range of from 0.01μm up to not greater than one-fourth the D50 grain size of the firstgrain mode based upon the total weight of the ceramic composition, (iii)at least 1 wt. % of a preservative component within the ceramiccomposition, based upon the total weight of the ceramic composition, thepreservative component selected from at least one of anyttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof,b) combining the first grain mode, the second grain mode, and thepreservative component to form a dispersed composition; and c) sinteringthe dispersed composition at a temperature of at least 1500° C. for atleast ten minutes to form a ceramic composition, wherein after sinteringthe ceramic composition has a porosity at ambient temperature in therange of from 5 to 45 vol %. The step b) of “combining” may furthercomprise the steps of: combining two of the preservative component, thefirst grain mode, and the second grain mode to form an initialcomposition; sintering the initial composition; grinding or otherwisereducing the initial composition to form a secondary composition;combining at least one of the preservative component, the first grainmode and the second grain mode with the secondary composition to formthe dispersed composition.

In other embodiments, the inventive methods include the step of shapingat least a portion of at least one of the dispersed composition and thesintered ceramic composition. The step of shaping may include, but isnot limited to, at least one of extruding, molding, forming, blowing,casting, pressing, drawing, rolling, milling, grinding, crushing,glazing, annealing, or combinations thereof. Forming or shaping may alsoinclude the step of controlling the shaping force and shaping processessuch that the porosity at ambient temperature, after sintering is withina range of from 5 to 45 vol % based upon the volume of the component.This may mean using less force than would otherwise be done in formingsuch component from a traditional ceramic material. According to thepresent invention, the formed component is also sintering at atemperature of from 1500° C. to 1800° C. for at least ten minutes, butmay be sintered for at least two hours at such temperature. Thesintered, formed component may thus demonstrate performance propertiesthat include a flexural strength of at least 6 kpsi and the normalizedthermal shock resistance rating is at least four. The sinteredcomponents may also be further annealed or heated at a temperature of atleast 1500° C. for at least two hours, wherein after such furtherheating the component has porosity at ambient temperature in the rangeof from 5 to 45 vol %, based upon the volume of the component. In manyof such embodiments of methods, the second grain mode comprises thepreservative component.

In still other variations, the present inventions include a thermalpyrolysis reactor for pyrolyzing a feedstock, the reactor including arefractory material comprising: (i) at least 20 wt. % of a first grainmode, the first grain mode including stabilized zirconia having a D50grain size in the range of from 5 to 2000 μm based upon the total weightof the refractory material, the stabilized zirconia including a matrixoxide stabilizer; (ii) at least 1 wt. % of a second grain mode having aD50 grain size in the range of from 0.01 μm up to not greater thanone-fourth the D50 grain size of the first grain mode zirconia, basedupon the total weight of the refractory material; and (iii) at least 1wt. % of a preservative component within the aggregate of at least oneof (a) the first grain mode stabilized zirconia, (b) the second grainmode, and (c) an optional another grain mode, the preservative componentcomprising at least one of an yttrium-containing compound, CaO, MgO,Y₂O₃, CeO₂, and mixtures thereof, wherein after sintering, the materialhas porosity at 20° C. of from 5 to 45 vol %. In many embodiments, thesecond grain mode further comprises fully stabilized zirconia and thefirst grain stabilized zirconia comprises partially stabilized zirconia.In other embodiments, the first grain mode includes stabilized zirconiahaving a D50 grain size in the range of from 5 to 800 μm. In still otherembodiments, the first grain mode stabilized zirconia is partiallystabilized zirconia and is stabilized by at least 6 wt. % of at leastone of an yttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, andmixtures thereof, based upon the weight of the first grain modestabilized zirconia. In various other embodiments, the first grain modestabilized zirconia is fully stabilized zirconia and is stabilized by atleast 14 wt. % (˜at least 8 mol %) of at least one of anyttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof,based upon the weight of the first grain stabilized zirconia.

According to still other embodiments of the inventive pyrolysis reactor,the refractory material comprises at least 10 wt. % of combined weightof the preservative component, the matrix oxide stabilizer, andoptionally a second grain mode stabilizer, based upon the total weightof the material. In some embodiments, the second grain mode comprises afully stabilized zirconia, the fully stabilized zirconia is stabilizedby at least 14 wt. % of a second grain mode zirconia stabilizer basedupon the weight of the second grain mode stabilized zirconia. In otheraspects, the second grain mode comprises at least 15 wt. % of combinedweight of second grain mode stabilizer and preservative component, basedupon the weight of the second grain mode. Alternatively, the secondgrain mode consists essentially of the preservative component, while instill other embodiments, the second grain mode consists of thepreservative component. According to other definitions, the inventionalso includes embodiments wherein the aggregate weight of the matrixoxide stabilizer, the preservative component, and an optional secondgrain mode stabilizer comprises at least 10 wt. % of the material, basedupon the total weight of the material. Preferably, the reactor materialcomprises a flexural strength of at least 6 kpsi and a normalizedthermal shock resistance rating of at least four, as defined herein. Insome variations of the reactor, the first grain mode stabilized zirconiacomprises at least 6 wt. % of matrix oxide stabilizer, the matrix oxidestabilizer comprising at least one of an yttrium-containing compound,CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof, based upon the weight of thefirst grain stabilized zirconia. The preservative component comprises atleast one of an yttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, andmixtures thereof.

The term “thermal pyrolysis reactor” is defined broadly to includesubstantially any high temperature apparatus capable of hosting thermalreactions therein at temperatures in excess of 1500° C. In someexemplary embodiments, the thermal pyrolysis reactor comprises at leastone of a regenerative pyrolysis reactor and a deferred combustionpyrolysis reactor. In alternative embodiments, the inventive materialsmay be provided with substantially any of the many known reactors,crackers, refractory, and other thermal apparatus. In many apparatus,the inventive reactor material is heated to a temperature of at least1500° C., but in other embodiments to temperatures in excess of 1600°C., 1700° C., 1800° C., and even in excess of 2000° C. The inventivematerials are also useful at temperatures of less than 1500° C., butabove such temperature is where the art has been in need of significantimprovement. Exemplary reactor components may include, for example, butare not limited to a honeycomb monolith having flow channels forconducting at least one of a pyrolysis reactant, a pyrolysis feed, and apyrolysis product through the monolith. Many components, such as thoseused in a reactor, may by design include flow channels that may beregarded as or referred to in some contexts as “void volume” throughwhich fluid passes as part of the function of the component. It isunderstood that flow channels and other such designed void volume is notconsidered to be part of the porosity of the ceramic. The ceramicporosity specified herein is specifically for the portion of thecomponent that does not carry flow; often referred to as the wall or thesolid portion of the component.

A reactive region is merely those regions of the reactor apparatus thatare exposed to the high temperatures and is not limited to directcontact with reaction components. The invention may include a step ofheating the reactive region by in-situ thermal reaction. The reactiveregion may be defined broadly to include substantially any heated orheat-exposed portion of the reactor, such as the reactor core where thereactions occur. The reactive region may be heated by substantially anythermal process, but preferably may be heated by in-situ thermalreaction, such as deferred combustion. In other aspects, the inventivereactor components may include reactor regions or components thatcomprise the inventive components and materials described herein, thatare also used quench the pyrolysis product to halt or interrupt thereaction kinetics.

In yet other aspects, the invention includes a process for themanufacture of a hydrocarbon product from a hydrocarbon feed using apyrolysis reactor, the process comprising the steps of: (a) providing apyrolysis reactor with a reactive region comprising a refractorymaterial comprising: (i) at least 20 wt. % of a first grain mode basedupon the total weight of the refractory material, the first grain modehaving a D50 grain size in the range of from 5 to 2000 μm, in someembodiments in the size range of from 5 to 800 μm, the stabilizedzirconia including a matrix oxide stabilizer; (ii) at least 1 wt. % of asecond grain mode having a D50 grain size in the range of from 0.01 μmup to not greater than one-fourth the D50 grain size of the first grainmode zirconia, based upon the total weight of the refractory material;and (iii) at least 1 wt. % of a preservative component within theaggregate of at least one of (a) the first grain mode stabilizedzirconia, (b) the second grain mode stabilized zirconia, and (c) anoptional another grain mode; wherein after sintering, the material hasporosity at 20° C. in the range of from 5 to 45 vol %; (b) heating thereactive region component to a temperature of at least 1500° C. tocreate a heated region; and (c) feeding a hydrocarbon feed into theheated region to pyrolyze the hydrocarbon feed and create a pyrolyzedhydrocarbon product. The inventive process also includes the step ofquenching the pyrolyzed hydrocarbon product to produce a quenchedhydrocarbon pyrolysis product. The process may also include the step ofheating the reactive region by in-situ thermal reaction. In someembodiments, the first grain mode includes stabilized zirconia having aD50 grain size in the range of from 5 to 800 μm.

In still other aspects the invention includes a process for forming aceramic component, the process including the steps of: a) preparing amixture comprising a multimodal ceramic grain distribution including;(i) at least 20 wt. % of first grain mode ceramic material, based uponthe total weight of the multimodal grain distribution, includingstabilized zirconia, the first grain mode comprising a D50 grain size inthe range of from 5 to 2000 μm, in some embodiments 5 to 800 μm, thestabilized zirconia including a matrix oxide stabilizer to stabilize thefirst grain stabilized zirconia; and (ii) at least 1 wt. % of secondgrain mode ceramic material comprising a D50 grain size in the range offrom 0.01 μm up to not greater than one-fourth the D50 grain size of thefirst grain mode, dispersed within the first grains, based upon thetotal weight of the multimodal grain distribution, the second grain modecomprising at least 1 wt. % of a preservative component based upon theweight of the second grain mode, to stabilize the first grain stabilizedzirconia; (b) forming the mixture into a shape; (c) sintering the shape;wherein after sintering, the component has porosity at ambienttemperature in the range of from 5 to 45 vol. %, based upon the volumeof the component. The process may also include the step of forming theshape, which further comprises using a shaping force, including alimited shaping force so as not to over compact the grains, such as butnot limited to molding, extruding, casting, drawing, compressing,cutting, milling, etc., to form the component shape.

EXAMPLE 1

Table 2 illustrates an exemplary multimodal ceramic mixture including acoarse grit mode of stabilized zirconia and second grit mode comprisedof yttria as a preservative component, resulting in a composite mixturehaving a bimodal grain distribution. The coarse grit mode (H. C.Starck's Amperit® 827.054) is agglomerated and sintered powder producedby spray-drying a suspension comprising fine powders, yttrium oxidestabilizer, and organic binder and subsequent sintering. The resultingcomposition for the coarse grit mode is a partially stabilized zirconia.The second grit mode consists essentially of a stabilizer oxidematerial, in this example yttrium oxide. The composition may alsoinclude lesser percentages of various secondary oxide materials, such asmay be present by virtue of manufacturing process additives or products,mere incidental presence, and/or as contaminants. The second grit modeyttrium oxide functions both as the second grit mode structuralcomponent in the prepared multimodal ceramic composition and also as apreservative component as it includes oxide material (stabilizer) thatis not initially actively involved in directly stabilizing any zirconiacrystal materials that are present. It has been learned that thepresence of the stabilizer within the second grit mode can act over anextended period of time to increase the activity of the stabilizerwithin the partially stabilized coarse grit mode to sustain thepartially stabilized crystal structure of the coarse grit mode.

TABLE 2 Company Grade Chemistry (wt. %) Size H. C. Amperit ® 87.6~89.6%ZrO₂: 21~65 μm Starck 827.054 Balance, Y₂O₃: 7.0~9.0%, (D50 = 30 μm)HfO₂: 2.0%, Al₂O₃: (Spherical 0.2%, Fe₂O₃: 0.3%, Particle) SiO₂: 0.5%,TiO₂: 0.4% Alfa Aesar Stock No. 99.9% Y₂O₃ 1.0 μm 44286 (CrystalliteSize)

Both the coarse and second grain modes comprise a ceramic stabilizer,but the second grain mode either comprises substantially (a) only apreservative component stabilizer such as a metal oxide or a pureelemental form, or (b) includes a stabilized ceramic as either (i)having a surplus of stabilizer above the amount required to stabilizethe second grit ceramic, the surplus as the preservative component or(ii) includes a preservative component stabilizer as a component of thesecond grit mode that is separate from and in addition to the stabilizedceramic within the second grit mode. In Example 1, zirconia ceramic isnot present in the second grain mode. In some embodiments, however,there may be grain modes present in the mixture that may or may notinclude zirconia or ceramics within such other modes.

Thus, 88.2 wt. % coarse grit mode of stabilized zirconia powder and 11.8wt. % second grit mode of substantially pure yttrium powder were mixedwith an organic binder for an extrusion process. (During sintering, thepure yttrium oxidizes into yttrium oxide or yttria.) Note that the 7.0to 9.0 wt. % Y₂O₃ only partially stabilizes the ZrO₂ in the coarse gritmode, thus providing a relatively strong and thermal shock resistantcoarse grit matrix. The mixed powder was extruded to fabricate a greenbody of about 1. 13 mm in thickness, 7.9 mm in width, and 100 mm inlength. The extruded green body was fired at 1500 ° C. for two hrs in anindustrial kiln to fabricate a sintered body.

Referring to FIG. 1, FIG. 1 a illustrates an SEM image of the sinteredbody processed according to this example, wherein the legend barrepresents 50 μm. In this image, spherical coarse grit mode ofstabilized zirconia have a D50 grain size of about 30 μm and the secondgrit mode crystals of substantially just yttria that are in the D50grain size of about 1.0 μm. The fine yttria grits are beneficiallylocated at the neck between adjacent coarse grits and provide thedesirable increase in density and enhanced bonding between coarse grits,while still affording the requisite porosity range. In this image,porosity appears dark and is desirably located at interspaces createdbetween coarse stabilized zirconia grits. The resultant sintered bodycomprised:

-   -   i) composite ceramic matrix comprising a bimodal grain        distribution including 88.2 wt. % coarse grit stabilized        zirconia with a D50 average grit size of about 30 μm; and 11.8        wt. % fine yttria with a D50 average grit size of about 1.0 μm.    -   ii) 23 vol % porosity    -   iii) Normalized thermal shock resistance=5.    -   iv) MOR flexural strength=6.4 kpsi

To ascertain the thermal stability of the zirconia ceramic compositionof this invention, the sintered body (1500° C., 2 hrs) was furtherannealed at 1800° C. for 100 hrs in a hydrogen atmosphere flowing at arate of 50 cc/min. A high temperature, high vacuum furnace was used forthis experiment. The 100 hrs of total exposure at 1800° C. was segmentedinto five heat cycles of 20 hrs each with cooling to ambient temperaturebetween each cycle. In each cycle, the sintered component was heated to1800° C. at a heating rate of 15° C./min, held at 1800° C. for 20 hrs,and then cooled to 50° C. at a cooling rate of 15° C./min. Five totalcycles were employed to simulate rapid start up and shut down processesand to investigate the resulting effect on thermal shock.

FIG. 2 b provides an SEM image of the fractured cross section of theannealed body after heating at 1800° C. for 100 hrs in a hydrogenatmosphere, wherein the legend bar represents 100 μm. In this image, thefirst mode grits of partially stabilized zirconia are in the D50 averagegrain size of about 50.0 μm, but the fine mode grits of yttria becomeyttria-rich stabilized zirconia and incorporate into the annealed matrixto provide an enhanced-strength bond between first mode grains. Porosityappears dark and uniformly distributed in the annealed body. Themeasured porosity of the sintered and annealed body is about 13 vol %.The measured properties of the annealed embodiment comprised:

-   -   i) 87 wt. % advanced dual oxide composite matrix    -   ii) 13 vol % porosity.    -   iii) Normalized thermal shock resistance rating is 5.    -   iv) MOR Flexural Strength is 7.1 kpsi

The resultant D50 grit size and porosity in the annealed body providemechanical strength and thermal shock resistance properties that arewithin the desired range for such properties. The annealed, yttria-rich,stabilized multimodal ceramic component resulted at least in part fromthe first modes' crystallization, the porosity, and multimodalcomposition. The yttria in the second grit mode maintains the enhancedstrength and shock resistance properties while simultaneously providingimproved chemical stability at high temperature.

EXAMPLE 2

A ceramic composition was prepared comprising 80 wt. % coarse grit mode(−149 μm particle size) of partially stabilized zirconia powder(including 4 wt. % CaO stabilizer, from Alfa Aesar) and 20 wt. % secondgrit mode (−10 μm particle size) of CaO powder (99.95 wt. %, from AlfaAesar) were dispersed with heptane in HDPE milling jar. The powders inheptane were mixed for 4 hours with Yttria Toughened Zirconia (YTZ)balls (10 mm diameter, from Tosoh Ceramics) in a ball mill at 100 rpm.The heptane was removed from the mixed powders by a RotoVap evaporator.The dried powder was compacted in a 40 mm diameter die in a hydraulicuniaxial press (SPEX 3630 Automated X-press) at 5,000 psi. The resultinggreen disc pellet was ramped up to 600° C. at 25° C./min in air and heldat 600° C. for 30 min for residual solvent removal. The disc was thenheated to 1600° C. in air and held at 1600° C. for 4 hours of sinteringand annealing. The temperature was then reduced to below 100° C. at −15°C./min. The resultant dual oxide composites comprised:

-   -   i) 67 wt. % coarse partially stabilized zirconia with D50 grain        size of about 80 μm.    -   ii) 16 wt. % fine CaO-rich oxide with D50 average grain size of        about 20 μm.    -   iii) 17 vol % porosity.    -   iv) Normalized thermal shock resistance=5.    -   v) MOR flexural strength=6.0 kpsi

EXAMPLE 3

A ceramic composition was prepared including 40 wt. % of coarse grit(−105+44 μm particle size range) of stabilized zirconia powder(including 10˜15% Y₂O₃ stabilizer, from Alfa Aesar), 40 wt. % of coarsegrit (−44 μm particle size range) of stabilized zirconia powder(containing 10˜15% Y₂O₃ stabilizer, from Alfa Aesar), and 20 wt. % ofsecond grit (1 μm average particle size) of Y₂O₃ powder (99.9%, fromAlfa Aesar) were dispersed with heptane in HDPE milling jar. The powderswere mixed in heptane for 4 hours with zirconia balls (10 mm diameter,from Tosoh Ceramics) in a ball mill at 100 rpm. The heptane was removedfrom the mixed powders by rotary evaporator. The dried powder wascompacted in a 40 mm diameter die in a hydraulic uniaxial press (SPEX3630 Automated X-press) at 5,000 psi. The resulting green disc pelletwas ramped up to 600° C. at 25° C./min in air and held at 600° C. for 30min for residual solvent removal. The disc was then heated to 1600° C.in air and held at 1600° C. for 4 hours for sintering. The temperaturewas then reduced to below 100° C. at minus 5° C./min. The resultantcomposites comprised:

-   -   i) 67 wt. % partially stabilized zirconia with a P50 grain size        of about 50 μm.    -   ii) 16 wt. % fine Y₂O₃-rich oxide with average grain size of        about 2 μm.    -   iii) 17 vol % porosity.    -   iv) Normalized thermal shock resistance=5.    -   v) MOR flexural strength=6.0 kpsi

EXAMPLE 4

About 143.0 grams of yttrium nitrate hexahydrate, Y(NO₃)₃.6H₂O, weredissolved in about 200 cc of ethanol. After a clear solution wasprepared, about 125.0 grams of coarse grit mode (−105+44 μm particlesize range) stabilized zirconia powder (containing 10˜15% Y₂O₃, fromAlfa Aesar) was added to the solution. The suspension was mixed forabout 10 hrs without milling media in a ball mill at 100 rpm. Theethanol was removed from the solution by heating on a hot plate. Thedried powder was ramped up to 900° C. at 25° C./min in air and held at900° C. for 2 hrs to decompose yttrium nitrate to yttria. The heattreated powder was ground by use of mortar and pestle. And the powderwas compacted in a 40 mm diameter die in a hydraulic uniaxial press(SPEX 3630 Automated X-press) at 5,000 psi. The resulting green discpellet was then heated to 1600° C. in air and held at 1600° C. for 4hours. The temperature was then reduced to below 100° C. at −15° C./min.The resultant advanced dual oxide composites comprised:

-   -   i) 58 wt. % coarse PSZ with average grain size of about 60 μm.    -   ii) 32 wt. % fine Y₂O₃-rich oxide with average grain size of        about 3 μm.    -   iii) 10 vol % porosity.    -   iv) Normalized thermal shock resistance=5.    -   v) MOR flexural strength=8.5 kpsi

EXAMPLE 5

Two commercially available, refractory grade monomodal zirconias(MgO-PSZ (“PSZ”=partially stabilized Zirconia) and CaO-PSZ) werecompared to the exemplary composite of previous Example 4. Firstcomparative composition included Zircoa's 3077 ceramic, which is a MgOpartially stabilized zirconia (2.6 wt. % MgO), and is a monomodal, firstmode grain size sintered composition having density of about 4.9 g/ccand porosity of about 14 %. It contains about 62 wt. % monoclinic phasezirconia crystals. In addition to MgO, it also contains some chemicalimpurities or secondary oxides, including about 1.2 wt. % SiO₂, 0.1 wt.% Al₂O₃, 0.1 wt. % CaO, 0.4 wt. % Fe₂O₃ and 0.2 wt. % TiO₂. The secondcomparative composition included Zircoa's 1661 ceramic, which is a CaOpartially stabilized zirconia (3.0 wt. % CaO), and is a monomodal, firstmode grain size sintered composition having density of about 4.1 g/ccand porosity of about 27 vol %. It contains about 24 wt. % monoclinicphase zirconia crystals. In addition to CaO, it also contains somechemical impurities or secondary oxides, including about 2.1 wt. %Al₂O₃, 0.4 wt. % SiO₂, 0.3 wt. % MgO, 0.1 wt. % Fe₂O₃ and 0.1 wt. %TiO₂. Each prepared comparative composition and the exemplarycomposition of Example 6 was exposed to a flowing hydrogen environmentat 1700° C. using a high temperature/high vacuum furnace. Aftercompletion of three heat cycles of 24 hours per cycle, the chemicalstability of each sample was determined by weight loss measurement ofthe specimen. As reflected in Table 3 below, the comparative MgO-PSZ hadthe highest weight loss (0.024 g/cm²), followed by the comparative CaOstabilized (0.008 g/cm²). However, the exemplary Y₂O₃ stabilized sampleaccording to Example 4 only reflected weight loss of (0.001 g/cm²),demonstrating the highest rate of retention of stabilizer. Thesignificant weight loss of two comparative zirconia materials wasderived from loss of the stabilizer. For instance, after the comparativeMgO-PSZ was exposed to a flowing hydrogen environment at 1700° C. in ahigh temperature/high vacuum furnace, the furnace chamber was filled upwith ultra fine needle-like particles. Scanning electron microscopy andenergy dispersive X-ray analysis confirmed that these particles werepure MgO. The exemplary sample also demonstrated the highest retainedflexural strength after completion of the test. Both comparative samplesalso demonstrated MOR flexural strength of less than the desirableminimum of 6.0 kpsi after exposure to the heat cycles.

TABLE 3 Normalized Flexural Weight Manufacturer/ Thermal Shock StrengthLoss Ceramics Trade Name Resistance (kpsi) (g/cm²) MgO-PSZZircoa/Comp.3077 5 5.0 0.024 (comparative) CaO-PSZ Zircoa/Comp.1661 54.8 0.008 (comparative) Example 4 Exemplary dual 5 8.5 0.001 oxidecomposite

EXAMPLE 6

An exemplary ceramic composition was prepared by mixing 60 wt. % ofcoarse grit of stabilized zirconia powder (H. C. Starck's Amperit®827.054 of Example 1), D50 30 μm, 30 wt. % of medium grit (4 μm D50particle size) of stabilized zirconia powder (TZ8Y, from Tosoh Co.), and10 wt. % of second grit (1 μm D50 particle size) of Y₂O₃ powder (99.9%,from Alfa Aesar). The mixed ceramic powder was further compounded intoan extrusion batch comprising an organic binder and a solvent. The batchwas then extruded into a green honeycomb body, dried and fired at about1650° C. to form a honeycomb monolith ceramic body. The resultant dualoxide composites comprised:

-   -   i) 60 wt. % partially stabilized zirconia with a D50 grain size        of 50 μm.    -   ii) 32 wt. % fine Y₂O₃-rich oxide with a D50 grain size of 2 μm.    -   iii) 8 vol % porosity.    -   iv) Normalized thermal shock resistance=4.    -   v) MOR flexural strength=9.5 kpsi

EXAMPLE 7

Another exemplary ceramic composition was prepared by mixing 70 wt. % of30 μm D50 coarse grit of partially stabilized zirconia powder (Zircoa1373 powder, including 8 wt. % Y₂O₃ stabilizer, from Zircoa Inc.) and 30wt. % of second grit (1 μm average particle size) of Y₂O₃ powder (99.9%,from Alfa Aesar). Additional 2 wt. % wax over the ceramic mix was alsoadded to provide green strength. The mixed ceramic batch was pressedinto a circular shape (10 cm diameter×3 cm height) and fired at 1600° C.for sintering. The resultant composites comprised:

-   -   i) 65 wt. % partially stabilized zirconia with a P50 grain size        of about 50 μm.    -   ii) 20 wt. % fine Y₂O₃-rich oxide with average grain size of        about 2 μm.    -   iii) 15 vol % porosity.    -   iv) Normalized thermal shock resistance=5.    -   v) MOR flexural strength=7.5 kpsi

EXAMPLE 8

500.0 grams of yttrium nitrate hexahydrate, Y(NO₃)₃.6H₂O, were dissolvedin 200 cc of deionized water to prepare a clear solution. A circularzirconia body made out of Zircoa 2290 (including 5 wt. % Y₂O₃stabilizer, from Zircoa Inc., refractory brick comprising fused andsintered grains of yttria stabilized zirconia) was dipped into thesolution, dried and sintered at 1600° C. for 4 hrs in air. Dipping andsintering process was repeated for 7 times until the circular zirconiabody gained about 30 wt. % in mass. After the final dipping andsintering, the resultant dual oxide composites comprised:

-   -   i) 60 wt. % coarse grit with a D50 grain size of about 100 μm.    -   ii) 25 wt. % fine Y₂O₃-rich oxide second grit with D50 grain        size of about 5 μm.    -   iii) 15 vol % porosity.    -   iv) Normalized thermal shock resistance=5.    -   v) MOR flexural strength=6.7 kpsi

While the present invention has been described and illustrated withrespect to certain embodiments, it is to be understood that theinvention is not limited to the particulars disclosed and extends to allequivalents within the scope of the claims. Unless otherwise stated, allpercentages, parts, ratios, etc. are by weight. Unless otherwise stated,a reference to a compound or component includes the compound orcomponent by itself as well as in combination with other elements,compounds, or components, such as mixtures of compounds. Further, whenan amount, concentration, or other value or parameter is given as a listof upper preferable values and lower preferable values, this is to beunderstood as specifically disclosing all ranges formed from any pair ofan upper preferred value and a lower preferred value, regardless ofwhether ranges are separately disclosed.

1. A refractory material comprising: (i) at least 20 wt. % of a firstgrain mode based upon the total weight of said refractory material, saidfirst grain mode comprising stabilized zirconia having a D50 grain sizein the range of from 5 to 2000 μm, said stabilized zirconia including amatrix oxide stabilizer; (ii) at least 1 wt. % of a second grain modehaving a D50 grain size in the range of from 0.01 μm up to not greaterthan one-fourth the D50 grain size of said first grain mode zirconia,based upon the total weight of said refractory material; and (iii) saidrefractory material comprising at least 1 wt. % of a preservativecomponent; wherein after sintering said material has porosity at 20° C.of from 5 to 45 vol %.
 2. The material of claim 1, wherein saidpreservative component is provided within one or more of (a) said firstgrain mode, (b) said second grain mode, and (c) an optional anothergrain mode, and said at least 1 wt. % is determined by the aggregate ofpreservative component within the refractory material.
 3. The materialof claim 1, wherein said material comprises at least 10 wt. % ofcombined weight of said preservative component, said matrix oxidestabilizer, and optionally a second grain mode zirconia stabilizer,based upon the total weight of said refractory material.
 4. The materialof claim 1, wherein said second grain mode comprises a fully stabilizedzirconia, said fully stabilized zirconia is stabilized by at least 14wt. % of a second grain mode zirconia stabilizer based upon the weightof said second grain mode fully stabilized zirconia.
 5. The material ofclaim 1, wherein said second grain mode comprises said preservativecomponent and a stabilized zirconia; and wherein each of saidpreservative component and said second grain mode zirconia stabilizercomprises substantially the same compounds as comprise said first grainmatrix oxide stabilizer.
 6. The material of claim 1, wherein said secondgrain mode comprises a fully stabilized zirconia, said second grainfully stabilized zirconia is stabilized by a second grain mode zirconiastabilizer.
 7. The material of claim 1, wherein the aggregate weight ofsaid matrix oxide stabilizer, said preservative component, and anoptional second grain mode zirconia stabilizer comprises at least 10 wt.% of said material, based upon the total weight of said material.
 8. Thecomponent of claim 1, wherein said second grain mode consistsessentially of said preservative component.
 9. The material of claim 1,wherein said ceramic component comprises a flexural strength (MOR) of atleast 6 kpsi and a normalized thermal shock resistance rating of atleast four.
 10. The material of claim 1, wherein said first grain modecomprises stabilized zirconia having a D50 grain size in the range offrom 5 μm to 800 μm.
 11. The material of claim 1, wherein said firstgrain mode stabilized zirconia comprises at least 6 wt. % of matrixoxide stabilizer, said matrix oxide stabilizer comprising at least oneof an yttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixturesthereof, based upon the weight of said first grain stabilized zirconia.12. The material of claim 1, wherein said preservative componentcomprises at least one of an yttrium-containing compound, CaO, MgO,Y₂O₃, CeO₂, and mixtures thereof.
 13. The material of claim 1, whereinsaid second grain mode comprises at least 14 wt. % of at least one of anyttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof,based upon the weight of said second grain mode.
 14. The material ofclaim 1, wherein said refractory material includes; (i) 20 to 50 wt. %of said first grain mode, based upon the total weight of said material;(ii) 1 to 80 wt. % of said second grain mode, based upon the totalweight of said material; and (iii) a combined total of at least 1 wt. %of said preservative component within at least one of said first grainmode, said second grain mode, and said optional another grain mode. 15.A stabilized refractory component for use with a pyrolysis reactor, saidcomponent comprising; (i) at least 20 wt. % of a first grain mode basedupon the total weight of said refractory component, said first grainmode including stabilized zirconia having a D50 grain size in the rangeof from 5 to 2000 μm, said stabilized zirconia including a matrix oxidestabilizer; (ii) at least 1 wt. % of a second grain mode having a D50grain size in the range of from 0.01 μm up to not greater thanone-fourth the D50 grain size of said first grain mode, dispersed withinsaid first grain mode, based upon the total weight of said refractorycomponent; and (iii) at least 1 wt. % of a preservative component withinthe aggregate of at least one of (a) said first grain mode, (b) saidsecond grain mode, and (c) an optional another grain mode, based uponthe total weight of said refractory component; wherein said componenthas porosity at 20° C. in the range of from 5 to 45 vol %.
 16. Thecomponent of claim 15, wherein said component comprises at least 10 wt.% of combined weight of said preservative component, said matrix oxidestabilizer, and optionally a second grain mode stabilizer, based uponthe total weight of said refractory component.
 17. The component ofclaim 15, wherein said second grain mode comprises a fully stabilizedzirconia, said fully stabilized zirconia is stabilized by at least 14wt. % of a second grain zirconia stabilizer based upon the weight ofsaid second grain stabilized zirconia.
 18. The component of claim 15,wherein said second grain mode comprises said preservative component anda stabilized zirconia; and wherein each of said preservative componentand said second grain zirconia stabilizer comprises substantially thesame compounds as comprise said first grain matrix oxide stabilizer. 19.The component of claim 15, wherein said first grain mode stabilizedzirconia has a D50 grain size in the range of from 5 to 800 μm.
 20. Thecomponents of claim 15, wherein second grain mode consists of saidpreservative component.
 21. The component of claim 15, wherein saidcomponent is at least one of spheres, beads, honeycomb materials, tubes,pipes, U-tubes, fluid mixers, nozzles, extruded monoliths, bricks,tiles, catalyst trays, reactor trays, tray components, and otherpyrolysis components.
 22. The component of claim 15, wherein saidcomponent comprises a flexural strength of at least 6 kpsi and anormalized thermal shock resistance rating of at least four.
 23. Thecomponent of claim 15, wherein said first grain mode stabilized zirconiacomprises at least 1 wt. % of matrix oxide stabilizer, said matrix oxidestabilizer comprising at least one of an yttrium-containing compound,CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof, based upon the weight ofsaid first grain stabilized zirconia.
 24. The component of claim 23,wherein said first grain mode stabilized zirconia comprises at least 6wt. % of said matrix oxide stabilizer.
 25. The component of claim 15,wherein said preservative component comprises at least one of anyttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof.26. The component of claim 15, wherein said second grain mode comprisesat least one of an yttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂,and mixtures thereof, based upon the weight of said second grain mode.27. The component of claim 15, wherein said first grain mode comprisespartially stabilized zirconia and said second grain mode comprises fullystabilized zirconia.
 28. A method of preparing a ceramic compositioncomprising the steps of: a) preparing a granular ceramic compositionincluding at least: (i) at least 20 wt. % of a first grain mode basedupon the total weight of said ceramic composition, said first grain modecomprising stabilized zirconia having a D50 grain size in the range offrom 5 to 2000 μm, said stabilized zirconia including a matrix oxidestabilizer; and (ii) at least 1 wt. % of a second grain mode having aD50 grain size in the range of from 0.01 μm up to not greater thanone-fourth the D50 grain size of said first grain mode based upon thetotal weight of said ceramic composition, (iii) at least 1 wt. % of apreservative component within the ceramic composition, based upon thetotal weight of said ceramic composition, said preservative componentselected from at least one of an yttrium-containing compound, CaO, MgO,Y₂O₃, CeO₂, and mixtures thereof, b) combining said first grain mode,said second grain mode, and said preservative component to form adispersed composition; and c) sintering said dispersed composition at atemperature of at least 1500° C. for at least ten minutes to form aceramic composition, wherein after sintering said ceramic compositionhas a porosity at ambient temperature in the range of from 5 to 45 vol%.
 29. The method of claim 28, wherein said step of combining furthercomprising the steps of: combining two of said preservative component,said first grain mode, and said second grain mode to form an initialcomposition; sintering said initial composition; grinding or otherwisereducing said initial composition to form a secondary composition;combining at least one of said preservative component, said first grainmode and said second grain mode with said secondary composition to formsaid dispersed composition.
 30. The method of claim 28, furthercomprising the step of shaping at least a portion of at least one ofsaid dispersed composition and said sintered ceramic composition. 31.The method of claim 28, wherein the step of shaping comprises at leastone of extruding, molding, forming, blowing, casting, pressing, drawing,rolling, milling, grinding, crushing, glazing, annealing, orcombinations thereof.
 32. The method of claim 28, wherein said secondgrain mode comprises said preservative component.
 33. The method ofclaim 28, wherein said second grain mode consists essentially of saidpreservative component.
 34. A thermal pyrolysis reactor for pyrolyzing afeedstock, said reactor including a refractory material comprising: (i)at least 20 wt. % of a first grain mode stabilized zirconia, said firstgrain mode having a D50 grain size in the range of from 5 to 2000 μmbased upon the total weight of said refractory material, said stabilizedzirconia including a matrix oxide stabilizer; (ii) at least 1 wt. % of asecond grain mode having a D50 grain size in the range of from 0.01 μmup to not greater than one-fourth the D50 grain size of said first grainmode zirconia, based upon the total weight of said refractory material;and (iii) at least 1 wt. % of a preservative component within theaggregate of at least one of (a) said first grain mode stabilizedzirconia, (b) said second grain mode, and (c) an optional another grainmode, said preservative component comprising at least one of anyttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof,wherein after sintering, said material has porosity at 20° C. of from 5to 45 vol %.
 35. The reactor of claim 34, wherein said second grain modefurther comprises fully stabilized zirconia and said first grainstabilized zirconia comprises partially stabilized zirconia.
 36. Thereactor of claim 34, wherein said first grain mode stabilized zirconiais partially stabilized zirconia and is stabilized by at least 6 wt. %of at least one of an yttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂,and mixtures thereof, based upon the weight of said first grain modestabilized zirconia.
 37. The reactor of claim 34, wherein said firstgrain mode stabilized zirconia is fully stabilized zirconia and isstabilized by at least 14 wt. % of at least one of an yttrium-containingcompound, CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof, based upon theweight of said first grain stabilized zirconia.
 38. The reactor of claim34, wherein said refractory material comprises at least 10 wt. % ofcombined weight of said preservative component, said matrix oxidestabilizer, and optionally a second grain mode stabilizer, based uponthe total weight of said material.
 39. The reactor of claim 34, whereinsaid second grain mode comprises a fully stabilized zirconia, said fullystabilized zirconia is stabilized by at least 14 wt. % of a second grainmode zirconia stabilizer based upon the weight of said second grain modestabilized zirconia.
 40. The reactor of claim 34, wherein said secondgrain mode comprises a fully stabilized zirconia and at least 1 wt. % ofpreservative component, based upon the total weight of said second grainmode.
 41. The thermal reactor of claim 34, wherein said second grainmode comprises at least 15 wt. % of combined weight of second grain modestabilizer and preservative component, based upon the weight of saidsecond grain mode.
 42. The thermal reactor of claim 34, wherein saidsecond grain mode consists essentially of said preservative component.43. The thermal reactor of claim 42, wherein the aggregate weight ofsaid matrix oxide stabilizer, said preservative component, and anoptional second grain mode stabilizer comprises at least 10 wt. % ofsaid material, based upon the total weight of said material.
 44. Thethermal reactor of claim 34, wherein said material comprises a flexuralstrength of at least 6 kpsi and a normalized thermal shock resistancerating of at least four.
 45. The thermal reactor of claim 34, whereinsaid first grain mode comprises stabilized zirconia having a D50 grainsize in the range of from 5 to 800 μm.
 46. The thermal reactor of claim34, wherein said first grain mode stabilized zirconia comprises at least6 wt. % of matrix oxide stabilizer, said matrix oxide stabilizercomprising at least one of an yttrium-containing compound, CaO, MgO,Y₂O₃, CeO₂, and mixtures thereof, based upon the weight of said firstgrain stabilized zirconia.
 47. The thermal reactor of claim 34, whereinsaid preservative component comprises at least one of anyttrium-containing compound, CaO, MgO, Y₂O₃, CeO₂, and mixtures thereof.48. The thermal reactor of claim 34, wherein said thermal pyrolysisreactor comprises at least one of a regenerative pyrolysis reactor and adeferred combustion pyrolysis reactor.
 49. The thermal reactor of claim34, wherein said reactor material is heated to a temperature of at least1500° C.
 50. The thermal reactor of claim 34, wherein said materialcomprises a honeycomb monolith having flow channels for conducting atleast one of a pyrolysis reactant, a pyrolysis feed, and a pyrolysisproduct through said monolith.
 51. The thermal reactor of claim 34,wherein said material comprises at least one of spheres, beads,honeycomb materials, tubes, pipes, U-tubes, fluid mixers, nozzles,extruded monoliths, bricks, tiles, catalyst trays, reactor trays, traycomponents, and other refractory components that are exposed to hightemperature.
 52. A process for the manufacture of a hydrocarbon productfrom a hydrocarbon feed using a pyrolysis reactor, the processcomprising the steps of: (a) providing a pyrolysis reactor with areactive region comprising a refractory material, said refractorymaterial comprising: (i) at least 20 wt. % of a first grain mode, saidfirst grain mode comprising stabilized zirconia having a D50 grain sizein the range of from 5 to 2000 μm based upon the total weight of saidrefractory material, said stabilized zirconia including a matrix oxidestabilizer; (ii) at least 1 wt. % of a second grain mode having a D50grain size in the range of from 0.01 μm up to not greater thanone-fourth the D50 grain size of said first grain mode zirconia, basedupon the total weight of said refractory material; and (iii) at least 1wt. % of a preservative component within the aggregate of at least oneof (a) said first grain mode, (b) said second grain mode, and (c) anoptional another grain mode; wherein after sintering, said material hasporosity at 20° C. in the range of from 5 to 45 vol %; (b) heating saidreactive region to a temperature of at least 1500° C. to create a heatedregion; and (c) feeding a hydrocarbon feed into said heated region topyrolyze said hydrocarbon feed and create a pyrolyzed hydrocarbonproduct.
 53. The process of claim 52, further comprising the step ofquenching said pyrolyzed hydrocarbon product to produce a quenchedhydrocarbon pyrolysis product.
 54. The process of claim 52, furthercomprising the step of heating said heated region by in-situ thermalreaction.